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Some early medical entomology. Athanasius Kircher’s illustration of the Italian tarantula
and the music prescribed as an antidote for the poison of its bite. (1643).

u HANDBOOK OF MEDICAL
ENTOMOLOGY

WM. A. RILEY, Ph.D.

Professor of Insect Morphology and Parasitology, Cornell University
and

O. A. JOHANNSEN, Ph.D.

Professor of Biology, Cornell University

ITHACA, NEW YORK
THE COMSTOCK PUBLISHING COMPANY

BY THE COMSTOCK PUBLISHING COMPANY,
ITHACA, N. Y.

Press of W. F. Humphrey
Geneva, N. Y.

PREFACE

T HE Handbook of Medical Entomology is the outgrowth of a
course of lectures along the lines of insect transmission and
dissemination of diseases of man given by the senior author
in the Department of Entomology of Cornell University during the
past six years. More specifically it is an illustrated revision and
elaboration of his “Notes on the Relation of Insects to Disease”
published January, 1912.

Its object is to afford a general survey of the field, and primarily
to put the student of medicine and entomology in touch with the
discoveries and theories which underlie some of the most important
modern work in preventive medicine. At the same time the older
phases of the subject—the consideration of poisonous and parasitic
forms—have not been ignored.

Considering the rapid shifts in viewpoint, and the development
of the subject within recent years, the authors do not indulge in any
hopes that the present text will exactly meet the needs of every
one specializing in the field,—still less do they regard it as complete
or final. The fact that the enormous literature of isolated articles is
to be found principally in foreign periodicals and is therefore difficult
of access to many American workers, has led the authors to hope
that a summary of the important advances, in the form of a reference
book may not prove unwelcome to physicians, sanitarians and
working entomologists, and to teachers as a text supplementing
lecture work in the subject.

Lengthy as is the bibliography, it covers but a very small fraction
of the important contributions to the subject. It will serve only to
put those interested in touch with original sources and to open up
the field. Of the more general works, special acknowledgment
should be made to those of Banks, Brumpt, Castellani and Chalmers,
Comstock, Hewitt, Howard, Manson, Mense, Neveau-Lemaire,
Nuttall, and Stiles.

To the many who have aided the authors in the years past, by
suggestions and by sending specimens and other materials, sincerest
thanks is tendered. This is especially due to their colleagues in
the Department of Entomology of Cornell University, and to Pro¬
fessor Charles W. Howard, Dr. John Uri Lloyd, Mr. A. H. Ritchie,
Dr. I. M. Unger, and Dr. Luzerne Coville.

Preface

They wish to express indebtedness to the authors and publishers
who have so willingly given permission to use certain illustrations.
Especially is this acknowledgment due to Professor John Henry
Comstock, Dr. L. O. Howard, Dr. Graham-Smith, and Professor
G. H. T. Nutt all. Professor Comstock not only authorized the use
of departmental negatives by the late Professor M. V. Slingerland
(credited as M. V. S.), but generously put at their disposal the illus¬
trations from the Manual for the Study of Insects and from
the Spider Book. Figures 5 and 111 are from Peter’s “Der Arzt
und die Heilkunft in der deutschen Vergangenheit.” It should be
noted that on examining the original, it is found that Gottfried’s
figure relates to an event antedating the typical epidemic of dancing
mania.

Cornell University,
January, 1915.

Wm. A. Riley.

0. A. JOHANNSEN.

ADDITIONS AND CORRECTIONS

vi line 11, for Heilkunft read Heilkunst.

18 line 2, for tarsi read tarsus.

32 line 21, and legend under fig. 23, for C. (Conorhinus)
abdominalis read Melanolestes abdominalis.

47 legend under figure for 33c read 34.

92 line 22 and 25, for sangiusugus read sanguisugus.

116 legend under fig. 83, for Graham-Smith read Manson.

136 line 10, from bottom, insert “ring” after “chitin”.

137 line 3, for meditatunda read meditabunda.

145 line 7, from bottom, for Rs read R s .

158 line 20, for have read has.

2T2 after the chapter heading insert “continued”.

219 line 10, from bottom, for Cornohinus read Conorhinus.

266 line 1, fig. 1581 refers to the female.

272 line 5, insert “palpus” before “and leg”.

281 line 6, for discodial read discoidal.

281 last line, insert “from” before “the”.

284 line 5, for “tubercle of” read “tubercle or”.

305 lines 19, 28, 44, page 306 lines 1, 9, 22, 27, 30, page 307 line 7,
page 309 lines 8, 11, for R 4 + 5 read
309 legend under fig. 168 add Bureau of Entomology.

312 line 36, for “near apex” read “of M r -f 2 .”.

313 running headj for Muscidas read Muscoidea.

314 line 29, for “distal section” read “distally M,+ 2 ”.

315 legend under fig. 172, for Pseudopyrellia read Orthellia,

for Lyperosia read Hasmatobia, for Umbana read urbana.
323 and 325 legends under the figures, add “After Dr. J. H.
Stokes”.

328 line 7 from bottom for Apiochaeta read Aphiochaeta.

■

CONTENTS

CHAPTER I

INTRODUCTION... 1-5

Early suggestions regarding the transmission of disease by insects.

The ways in which arthropods may affect the health of man.

CHAPTER II

ARTHROPODS WHICH ARE DIRECTLY POISONOUS. 6-56

The Araneida, or Spiders.

The tarantulas. Bird spiders. Spiders of the genus Latrodectus. Other
venomous spiders. Summary.

The Pedipalpida, or whip-scorpions.

The Scorpionida, or true scorpions.

The Solpugida, or solpugids.

The Acarina, or mites and ticks.

The Myriapoda, or centipedes and millipedes.

The Hexapoda, or true insects.

Piercing or biting insects poisonous to man.

Hemiptera, or true bugs.

The Notonectidee or back-swimmers. Belostomidae or giant water-
bugs. Reduviidae, or assassin bugs. Other Hemiptera reported
as poisonous to man.

Diptera; the midges, mosquitoes and flies.

Stinging insects.

Apis mellifica, the honey bee. Other stinging forms.

Nettling insects.

Lepidoptera, or butterflies and moths. Relief from poisoning by nettling
larvae.

Vescicating insects and those possessing other poisons in their blood plasma.
The blister beetles. Other cryptotoxic insects.

CHAPTER III

PARASITIC ARTHROPODS AFFECTING MAN. 57-130

Acarina, or mites.

The Trombidiidse, or harvest mites.

The Ixodoidea, or ticks.

Argasidae. Ixodidae. Treatment of tick bites.

The mites.

Dermanyssidae. Tarsonemidae. Sarcoptidae, the itch mites. Demode-
cidae, the follicle mites.

Hexapoda, or true insects.

Siphunculata, or sucking lice.

Hemiptera.

VIII

Contents

The bed-bug. Other bed-bugs.

Parasitic Diptera, or flies.

Psychodidae, or moth flies. Phlebotominae. Culicidae, or mosquitoes.
Simuliidae, or black-flies. Chironomidae, or midges. Tabanidae, or
horse-flies. Leptidae or snipe-flies. Oestridas, or bot-flies. Muscidae,
the stable-fly and others.

Siphonaptera, or fleas.

The fleas affecting man, the dog, cat, and rat.

The true chiggers, or chigoes.

CHAPTER IV

ACCIDENTAL OR FACULTATIVE PARASITES. 131-143

Acarina, or mites.

Myriapoda, or centipedes and millipedes.

Lepidopterous larvae.

Coleoptera, or beetles.

Dipterous larvae causing myiasis.

Piophila casei, the cheese skipper. Chrysomyia macellaria, the screw-
worm fly. Calliphorinae, the blue-bottles. Muscinae, the house or
typhoid fly, and others. Anthomyiidas, the lesser house-fly and others.
Sarcophagidae, the flesh-flies.

CHAPTER V

ARTHROPODS AS SIMPLE CARRIERS OF DISEASE. 144-163

The house or typhoid fly as a carrier of disease.

Stomoxys calcitrans, the stable-fly.

Other arthropods which may serve as simple carriers of pathogenic organisms.

CHAPTER VI

ARTHROPODS AS DIRECT INOCULATORS OF DISEASE GERMS 164-174

Some illustrations of direct inoculations of disease germs by arthropods.

The r61e of fleas in the transmission of the plague.

CHAPTER VII

ARTHROPODS AS ESSENTIAL HOSTS OF PATHOGENIC ORGAN¬
ISMS . 175-185

Insects as intermediate hosts of tape-worms.

Arthropods as intermediate hosts of nematode worms. Filariasis and mosqui¬
toes.

Other nematode parasites of man and animals.

CHAPTER VIII

ARTHROPODS AS ESSENTIAL HOSTS OF PATHOGENIC PRO¬
TOZOA . 186-211

Mosquitoes and malaria.

Mosquitoes and yellow fever.

Contents

CHAPTER IX

ARTHROPODS AS ESSENTIAL HOSTS OF PATHOGENIC PRO¬
TOZOA . 212-229

Insects and trypanosomiases.

Fleas and lice as carriers of Trypanosoma lewisi.

Tsetse-flies and nagana.

Tsetse-flies and sleeping sickness in man.

South American trypanosomiasis.

Leishmanioses and insects.

Ticks and diseases of man and animals.

Cattle tick and Texas fever.

Ticks and Rocky Mountain Spotted fever of man.

CHAPTER X

ARTHROPODS AS ESSENTIAL HOSTS OF PATHOGENIC PROTO¬
ZOA (Continued) . 230-240

Arthropods and Spirochaetoses of man and animals.

African relapsing fever of man.

European relapsing fever.

North African relapsing fever of man.

Other types of relapsing fever of man.

Spirochetosis of fowls.

Other spirochaete diseases of animals.

Typhus fever and lice.

CHAPTER XI

SOME POSSIBLE, BUT IMPERFECTLY KNOWN CASES OF

ARTHROPOD TRANSMISSION OF DISEASE . 241-256

Infantile paralysis, or acute anterior poliomyelitis.

Pellagra. Leprosy. Verruga peruviana. Cancer.

CHAPTER XII

KEYS TO THE ARTHROPODS NOXIOUS TO MAN .

Crustacea.

Myriapoda, or centipedes and millipedes.

Arachnida (Orders of).

Acarina or ticks.

Hexapoda (Insecta).

Siphunculata and Hcmiptera (lice and true bugs).

Diptera (mosquitoes, midges, and flies).

Siphonaptera (fleas).

APPENDIX

Hydrocyanic acid gas against household insects.

Proportion of ingredients. A single room as an example,
large house. Precautions.

Lesions produced by the bite of the black-fly.

BIBLIOGRAPHY .

INDEX .

257-317

. 318-320

Fumigating a

. 321-326

. 327-340

. 341-348

CHAPTER I.

INTRODUCTION

EARLY SUGGESTIONS REGARDING THE TRANSMISSION OF DISEASE

BY INSECTS

Until very recent years insects and their allies have been considered
as of economic importance merely in so far as they are an annoyance
or direct menace to man, or his flocks and herds, or are injurious to
his crops. It is only within the past fifteen years that there has
sprung into prominence the knowledge that in another and much more
insiduous manner, they may be the enemy of mankind, that they
may be among the most important of the disseminators of disease.
In this brief period, such knowledge has completely revolutionized
our methods of control of certain diseases, and has become an import¬
ant weapon in the fight for the conservation of health.

It is nowhere truer than in the case under consideration that how¬
ever abrupt may be their coming into prominence, great move¬
ments and great discoveries do not arise suddenly. Centuries ago
there was suggested the possibility that insects were concerned with
the spread of disease, and from time to time there have appeared keen
suggestions and logical hypotheses along this line, that lead us to
marvel that the establishment of the truths should have been so long
delayed.

One of the earliest of these references is by the Italian physician,
Mercurialis, who lived from 1530 to 1607, during a period when
Europe was being ravaged by the dread “black death”, or plague.
Concerning its transmission he wrote: “There can be no doubt that
flies feed on the internal secretions of the diseased and dying, then,
flying away, they deposit their excretions on the food in neighboring
dwellings, and persons who eat of it are thus infected.”

It would be difficult to formulate more clearly this aspect of the
facts as we know them to-day, though it must always be borne in
mind that we are prone to interpret such statements in the light of
present-day knowledge. Mercurialis had no conception of the animate
nature of contagion, and his statement was little more than a lucky
guess.

Much more worthy of consideration is the approval which was
given to his view by the German Jesuit, Athanasius Kircher in 1658.

Introduction

One cannot read carefully his works without believing that long
before Leeuwenhook’s discovery, Kircher had seen the larger species of
bacteria. Moreover, he attributed the production of disease to these
organisms and formulated, vaguely, to be sure, a theory of the animate
nature of contagion. It has taken two and a half centuries to
accumulate the facts to prove his hypothesis.

The theory of Mercurialis was not wholly lost sight of, for in the
medical literature of the eighteenth century there are scattered
references to flies as carriers of disease. Such a view seems even to
have been more or less popularly accepted, in some cases. Gudger
(1910), has pointed out that, as far back as 1769, Edward Bancroft,
in “An Essay on the Natural History of Guiana in South America,”
wrote concerning the contagious skin-disease known as “Yaws”:
“It is usually believed that this disorder is communicated by the flies
who have been feasting on a diseased object, to those persons who have
sores, or scratches, which are uncovered; and from many observa¬
tions, I think this is not improbable, as none ever receive this disorder
whose skins are whole.”

Approaching more closely the present epoch, we find that in 1848,
Dr. Josiah Nott, of Mobile, Alabama, published a remarkable
article on the cause of yellow fever, in which he presented “reasons for
supposing its specific cause to exist in some form of insect life.”
As a matter of fact, the bearing of Nott’s work on present day ideas
of the insect transmission of disease has been very curiously overrated.
The common interpretation of his theory has been deduced from a few
isolated sentences, but his argument appears quite differently when
the entire article is studied. It must be remembered that he wrote at
a period before the epoch-making discoveries of Pasteur and before
the recognition of micro-organisms as factors in the cause of disease.
His article is a masterly refutation of the theory of “malarial” origin
of “all the fevers of hot climates,” but he uses the term “insect” as
applicable to the lower forms of life, and specific references to “mos¬
quitoes,” “aphids,” “cotton-worms,” and others, are merely in the
way of similes.

But, while Nott’s ideas regarding the relation of insects to yellow
fever were vague and indefinite, it was almost contemporaneously
that the French physician, Louis Daniel Beauperthuy argued in the
most explicit possible manner, that yellow fever and various others
are transmitted by mosquitoes. In the light of the data which were
available when he wrote, in 1853, it is not surprising that he erred by

Early Suggestions

thinking that the source of the virus was decomposing matter which
the mosquito took up and accidentally inoculated into man. Beau-
perthuy not only discussed the role of mosquitoes in the transmission
of disease, but he taught, less clearly, that house-flies scatter patho¬
genic organisms. It seems that Boyce (1909) who quotes extensively
from this pioneer work, does not go too far when he says “It is Dr.
Beauperthuy whom we must regard as the father of the doctrine of
insect-borne disease.”

In this connection, mention must be made of the scholarly article
by the American physician, A. F. A. King who, in 1883, brought
together an all but conclusive mass of argument in support of his
belief that malaria was caused by mosquitoes. At about the same
time, Finley, of Havana, was forcefully presenting his view that the
mosquito played the chief r 61 e in the spread of yellow fever.

To enter more fully into the general historical discussion is beyond
the scope of this book. We shall have occasion to make more
explicit references in considering various insect-borne diseases.
Enough has been said here to emphasize that the recognition of
insects as factors in the spread of disease was long presaged, and that
there were not wanting keen thinkers who, with a background of
present-day conceptions of the nature of disease, might have been in
the front rank of investigators along these lines.

THE WAYS IN WHICH ARTHROPODS MAY AFFECT THE HEALTH

OF MAN

When we consider the ways in which insects and their allies may
affect the health of man, we find that we may treat them under three
main groups:

A. They may be directly poisonous. Such, for example, are the
scorpions, certain spiders and mites, some of the predaceous bugs,
and stinging insects. Even such forms as the mosquito deserve
some consideration from this viewpoint.

B. They may be parasitic, living more or less permanently on
or in the body and deriving their sustenance from it.

Of the parasitic arthropods we may distinguish, first, the true
parasites, those which have adopted and become confirmed in the
parasitic habit. Such are the itch mites, the lice, fleas, and the
majority of the forms to be considered as parasitic.

In addition to these, we may distinguish a group of accidental, or
facultative parasites, species which are normally free-living, feeding on

Introduction

decaying substances, but which when accidentally introduced into
the alimentary canal or other cavities of man, may exist there
for a greater or less period. For example, certain fly larvas, or mag¬
gots, normally feeding in putrifying meat, have been known to occur
as accidental or facultative parasites in the stomach of man.

C. Finally, and most important, arthropods may be trans¬
mitters and disseminators of disease. In this capacity they may
function in one of three ways; as simple carriers , as direct inoculators ,
or as essential hosts of disease germs.

As simple carriers, they may, in a wholly incidental manner,
transport from the diseased to the healthy, or from filth to food,
pathogenic germs which cling to their bodies or appendages. Such,
for instance, is the relation of the house-fly to the dissemination of
typhoid.

As direct inoculators, biting or piercing species may take up from
a diseased man or animal, germs which, clinging to the mouth parts,
are inoculated directly into the blood of the insect’s next victim. It
it thus that horse-flies may occasionally transmit anthrax. Similarly,
species of spiders and other forms which are ordinarily perfectly
harmless, may accidentally convey and inoculate pyogenic bacteria.

It is as essential hosts of disease germs that arthropods play their
most important role. In such cases an essential part of the life cycle
of the pathogenic organism is undergone in the insect. In other
words, without the arthropod host the disease-producing organism
cannot complete its development. As illustrations may be cited the
relation of the Anopheles mosquito to the malarial parasite, and the
relation of the cattle tick to Texas fever.

A little consideration will show that this is the most important of
the group. Typhoid fever is carried by water or by contaminated
milk, and in various other ways, as well as by the house-fly. Kill all
the house-flies and typhoid would still exist. On the other hand,
malaria is carried only by the mosquito, because an essential part of
the development of the malarial parasite is undergone in this insect.
Exterminate all of the mosquitoes of certain species and the dis¬
semination of human malaria is absolutely prevented.

Once an arthropod becomes an essential host for a given parasite
it may disseminate infection in three different ways:

i. By infecting man or animals who ingest it. It is thus, for
example, that man, dog, or cat, becomes infected with the double-
pored dog tapeworm, Dipylidium caninwn. The cysticercoid stage

Arthropods and Man

occurs in the dog louse, or in the dog or cat fleas, and by accidentally
ingesting the infested insect the vertebrate becomes infested. Simi¬
larly, Hymenolepis diminuta, a common tapeworm of rats and mice,
and occasional in man, undergoes part of its life cycle in various meal-
infesting insects, and is accidentally taken up by its definitive host.
It is very probable that man becomes infested- with Dracunculus
( Filaria ) medinensis through swallowing in drinking water, the
crustacean, Cyclops, containing the larvae of this worm.

2. By infecting man or animals on whose skin or mucous mem¬
branes the insect host may be crushed or may deposit its excrement.
The pathogenic organism may then actively penetrate, or may be
inoculated by scratching. The causative organism of typhus fever
is thus transmitted by the body louse.

3. By direct inoculation by its bite, the insect host may transfer
the parasite which has undergone development within it. The
malarial parasite is thus transferred by mosquitoes; the Texas fever
parasite by cattle ticks.

CHAPTER II.

ARTHROPODS WHICH ARE DIRECTLY POISONOUS

Of all the myriads of insects and related forms, a very few are of
direct use to man, some few others have forced his approbation on
account of their wonderful beauty, but the great hordes of them are
loathed or regarded as directly dangerous. As a matter of fact, only
a very small number are in the slightest degree poisonous to man or
to the higher animals. The result is that entomologists and lovers
of nature, intent upon dissipating the foolish dread of insects, are
sometimes inclined to go to the extreme of discrediting all statements
of serious injury from the bites or stings of any species.

Nevertheless, it must not be overlooked that poisonous forms do
exist, and they must receive attention in a consideration of the ways
in which arthropods may affect the health of man. Moreover, it
must be recognized that “what is one man’s meat, is another man’s
poison,” and that in considering the possibilities of injury we must not
ignore individual idiosyncrasies. Just as certain individuals may be
poisoned by what, for others are common articles'of food, so some
persons may be abnormally susceptible to insect poison. Thus, the
poison of a bee sting may be of varying severity, but there are individ¬
uals who are made seriously sick by a single sting, regardless of the
point of entry. Some individuals scarcely notice a mosquito bite,
others find it very painful, and so illustrations of this difference in
individuals might be multiplied.

In considering the poisonous arthropods, we shall take them up by
groups. The reader who is unacquainted with the systematic rela¬
tionship of insects and their allies is referred to Chapter XII. No
attempt will be made to make the lists under the various headings
exhaustive, but typical forms will be discussed.

ARANEIDA OR SPIDERS

Of all the arthropods there are none which are more universally
feared than are the spiders. It is commonly supposed that the
majority, if not all the species are poisonous and that they are aggres¬
sive enemies of man and the higher animals, as well as of lower forms.

That they really secrete a poison may be readily inferred from the
effect of their bite upon insects and other small forms. Moreover,

Araneida or Spiders

Head of a spider showing
poison gland ( c ) and its re¬
lation to the chelicera (a).

the presence of definite and well-developed poison glands can easily
be shown. They occur as a pair of pouches (fig. i) lying within the
cephalothorax and connected by a delicate
duct with a pore on the claw of the chelicera,
or so-called “mandible” on the convex surface
of the claw in such a position that it is not
plugged and closed by the flesh of the victim.

The glands may be demonstrated by slowly
and carefully twisting off a chelicera and
pushing aside the stumps of muscles at its
base. By exercising care, the chitinous wall
of the chelicera and its claw may be broken
away and the duct traced from the gland to its outlet. The inner
lining of the sac is constituted by a highly developed glandular
epithelium, supported by a basement membrane of connective
tissue and covered by a muscular layer, (fig. 2). The muscles, which
are striated, are spirally arranged (fig. 1), and are doubtless under
control of the spider, so that the amount of poison to be injected into
a wound may be varied.

The poison itself, according to Kobert (1901), is a clear, colorless
fluid, of oily consistency, acid reaction, and very bitter taste. After
the spider has bitten two or three times, its supply is exhausted and
therefore, as in the case of snakes, the poison of the bite decreases
quickly with use, until it is null. To what extent the content of the
poison sacs may contain blood serum or, at least, active principles of
serum, in addition to a specific poison formed by the poison glands
themselves, Kobert regards as an open question. He believes that
the acid part of the poison, if really present,
is formed by the glands and that,
in the case of some spiders, the
ferment-like, or better, active
toxine, comes from the blood.

But there is a wide difference
between a poison which may kill
an insect and one which is harm¬
ful to men. Certain it is that
there is no lack of popular belief
and newspaper records of fatal
cases, but the evidence regarding the possibility of fatal or even vein-
serious results for man is most contradictory. For some years,
we have attempted to trace the more circumstantial newspaper

3. Chelicera of
spider.

Section through a venom
gland of Latrodectus
13 -guttatus showing
the peritoneal, muscu¬
lar and epithelial layers.
After Bordas.

Poisonous Arthropods

accounts, which have come to our notice, of injury by North
American species. The results have served, mainly, to empha¬
size the straits to which reporters are sometimes driven when
there is a dearth of news. The accounts are usually vague and lack¬
ing in any definite clue for locating the supposed victim. In the
comparatively few cases where the patient, or his physician, could
be located, there was either no claim that the injury wa% due to
spider venom, or there was no evidence to support the belief.
Rarely, there was evidence that a secondary blood poisoning, such
as might be brought about by the prick of a pin, or by any mechani¬
cal injury, had followed the bite of a spider. Such instances have

no bearing on the question of the
venomous nature of these forms.

The extreme to which unreason¬
able fear of the bites of spiders
influenced the popular mind was
evidenced by the accepted explana¬
tion of the remarkable dancing
mania, or tarantism, of Italy during
the Middle Ages. This was a ner¬
vous disorder, supposed to be due
to the bite of a spider, the European
tarantula (fig. 4), though it was
also, at times, attributed to the

4. The Italian tarantula (Lycosa tarantula), bite of the SCOrpion. In its tvpical

form, it was characterized by so
great a sensibility to music that under its influence the victims
indulged in the wildest and most frenzied dancing, until they sank
to the ground utterly exhausted and almost lifeless. The profuse
perspiring resulting from these exertions was supposed to be the
only efficacious remedy for the disease. Certain forms of music
were regarded as of especial value in treating this tarantism, and
hence the name of “ tarantella” was applied to them. Our frontis¬
piece, taken from Athanasius Kircher’s Magnes sive de Arte Magnetica,
1643 ed., represents the most commonly implicated spider and illus¬
trates some of what Fabre has aptly designated as “medical
choreography.”

The disease was, in reality, a form of hysteria, spreading by sym¬
pathy until whole communities were involved, and was paralleled by
the outbreaks of the so-called St. Vitus’s or St. John’s dance, which

Araneida or Spiders

swept Germany at about the same time (fig. 5). The evidence that
the spider was the cause of the first is about as conclusive as is that
of the demoniacal origin of the latter. The true explanation of the
outbreaks is doubtless to be found in the depleted physical and mental
condition of the people, resulting from the wars and the frightful
plagues which devastated all Europe previous to, and during these
times. An interesting discussion of these aspects of the question is to
be found in Hecker.

5 . Dancing mania. Illustration from Johann Ludwig Gottfried's Chronik. 1632.

So gross has been the exaggeration and so baseless the popular fear
regarding spiders that entomologists have been inclined to discredit
all accounts of serious injury from their bites. Not only have the
most circumstantial of newspaper accounts proved to be without
foundation but there are on record a number of cases where the bite
of many of the commoner species have been intentionally provoked
and where the effect has been insignificant. Some years ago the
senior author personally experimented with a number of the largest of
our northern species, and with unexpected results. The first surprise
was that the spiders were very unwilling to bite and that it required a
considerable effort to get them to attempt to do so. In the second

Poisonous Arthropods

place, most of those experimented with were unable to pierce the skin
of the palm or the back of the hand, but had to be applied to the thin
skin between the fingers before they were able to draw blood. Unfor¬
tunately, no special attempt was made to determine, at the time, the
species experimented with, but among them were Theridion tepi-
dariorum, Miranda aurantia (Argiopa ), Metargiope trifasciata, Marxia
stellata, Aranea trifolium, Misumena vatia, and Agelena ncevia. In
no case was the bite more severe than a pin prick and though in some
cases the sensation seemed to last longer, it was probably due to the
fact that the mind was intent upon the experiment.

Similar experiments were carried out by Blackwell (1855), who
believed that in the case of insects bitten, death did not result any

6. An American tarantula (Eurypelma hentzii). Natural size. After Comstock

more promptly than it would have from a purely mechanical injury of
equal extent. He was inclined to regard all accounts of serious
injury to man as baseless. The question cannot be so summarily
dismissed, and we shall now consider some of the groups which have
been more explicitly implicated.

The Tarantulas. — In popular usage, the term “ tarantula ” is
loosely applied to any one of a number of large spiders. The famous
tarantulas of southern Europe, whose bites were supposed to cause the
dancing mania, were Lycosidae, or wolf-spiders. Though various
species of this group were doubtless so designated, the one which
seems to have been most implicated was Lycosa tarantula (L.),
(fig. 4). On the other hand, in this country, though there are many
Lycosidae, the term “tarantula” has been applied to members of the
superfamily Avicularoidea (fig. 6), including the bird-spiders.

Of the Old World Lycosidae there is no doubt that several species
were implicated as the supposed cause of the tarantism. In fact, as
we have already noted, the blame was sometimes attached to a scor-

The Tarantulas

pion. However, there seems to be no doubt that most of the accounts
refer to the spider known as Lycosa tarantula.

There is no need to enter into further details here regarding the
supposed virulence of these forms, popular and the older medical
literature abound in circumstantial accounts of the terrible effects of
the bite. Fortunately, there is direct experimental evidence which
bears on the question.

Fabre induced a common south European wolf-spider, Lycosa
narbonensis, to bite the leg of a young sparrow, ready to leave the
nest. The leg seemed paralyzed as a result of the bite, and though
the bird seemed lively and clamored for food the next day, on the
third day it died. A mole, bitten on the nose, succumbed after thirty-
six hours. From these experiments Fabre seemed justified in his
conclusion that the bite of this spider is not an accident which man
can afford to treat lightly. Unfortunately, there is nothing in the
experiments, or in the symptoms detailed, to exclude the probability
that the death of the animals was the result of secondary infection.

As far back as 1693, as we learn from the valuable account of
Robert, (1901), the Italian physician, Sanguinetti allowed himself to
be bitten on the arm by two tarantulas, in the presence of witnesses.
The sensation was equivalent to that from an ant or a mosquito bite
and there were no other phenomena the first day. On the second day
the wound was inflamed and there was slight ulceration. It is clear
that these later symptoms were due to a secondary infection. These
experiments have been repeated by various observers, among whom
may be mentioned Leon Dufour, Josef Erker and Heinzel, and with
the similar conclusion that the bite of the Italian tarantula ordinarily
causes no severe symptoms. In this conclusion, Robert, though
firmly convinced of the poisonous nature of some spiders, coincides.
He also believes that striking symptoms may be simulated or arti¬
ficially induced by patients in order to attract interest, or because
they have been assured that the bite, under all circumstances, caused
tarantism.

The so-called Russian tarantula, Trochosa singoriensis (fig. 7), is
much larger than the Italian species, and is much feared. Robert
carried out a series of careful experiments with this species and his
results have such an important bearing on the question of the venom¬
ous nature of the tarantula that we quote his summary. Experi¬
menting first on nearly a hundred living specimens of Trochosa
singoriensis from Crimea he says that:

Poisonous Arthropods

“The tarantulas, no matter how often they were placed on the
skin, handled, and irritated, could not be induced to bite either myself,
the janitor, or the ordinary experimental animals. The objection
that the tarantulas were weak and indifferent cannot stand, for as
soon as I placed two of them on the shaved skin of a rabbit, instead of
an attack on the animal, there began a furious battle between the
two spiders, which did not cease until one of the two was killed.”

“Since the spiders would not
bite, I carefully ground up the
fresh animals in physiological
salt solution, preparing an extract
which must have contained, in
solution, all of the poisonous
substance of their bodies. While
in the case of Latrodectus, as we
shall see, less than one specimen
sufficed to yield an active extract,
I have injected the filtered extract
of six fresh Russian tarantulas,
of which each one was much
heavier than an average Latro¬
dectus , subcutaneously and into
the jugular vein of various cats
without the animals dying or
showing any special symptoms.
On the basis of my experiments I can therefore only say that the
quantity of the poison soluble in physiological salt solution, even
when the spiders are perfectly fresh and well nourished, is very
insignificant. That the poison of the Russian tarantula is not
soluble in physiological salt solution, is exceedingly improbable.
Moreover, I have prepared alcoholic extracts and was unable to
find them active. Since the Russian spider exceeds the Italian in
size and in intensity of the bite, it seems very improbable to me that
the pharmacological test of the Italian tarantula would yield
essentially other results than those from the Russian species.”

To the Avicularoidea belong the largest and most formidable
appearing of the spiders and it is not strange that in the New World
they have fallen heir to the bad reputation, as well as to the name of
the tarantula of Europe. In this country they occur only in the
South or in the far West, but occasionally living specimens are brought

The Tarantulas

to our northern ports in shipments of bananas and other tropical
produce, and are the source of much alarm. It should be mentioned,
however, that the large spider most frequently found under such cir¬
cumstances is not a tarantula at all, but one of the Heteropodidae, or
giant crab-spiders, (fig. 8).

In spite of their prominence and the fear which they arouse there
are few accurate data regarding these American tarantulas. It has

8. The giant crab-spider or banana spider (Heteropoda venatoria).

Natural size. After Comstock.

often been shown experimentally that they can kill small birds and
mammals, though it is doubtful if these form the normal prey of any
of the species, as has been claimed. There is no question but that
the mere mechanical injury which they may inflict, and the consequent
chances of secondary infection, justify, in part, their bad reputation.
In addition to the injury from their bite, it is claimed that the body
hairs of several of the South American species are readily detached
and are urticating.

Recently, Phisalix (1912) has made a study of the physiological
effects of the venom of two Avicularoidea, Phormictopus carcerides
Pocock, from Haiti and Cteniza sauvagei Rossi, from Corsica. The
glands were removed aseptieally and ground up with fine, sterilized
sand in distilled water. The resultant liquid was somewhat viscid,
colorless, and feebly alkaline. Injected into sparrows and mice the

Poisonous Arthropods

extract of Phormictopus proved very actively poisonous, that from a
single spider being sufficient to kill ten sparrows or twenty-mice. It
manifested itself first and, above all, as a narcotic, slightly lowering
the temperature and paralyzing the respiration. Muscular and
cardiac weakening, loss of general sensibility, and the disappearance
of reflexes did not occur until near the end. The extract from Cteniza
was less active and, curiously enough, the comparative effect on
sparrows and on mice was just reversed.

Spiders of the Genus Latrodectus. —While most of the popular

accounts of evil effects from the bites of spiders will not stand investi¬
gation, it is a significant fact that, the world over, the best authentica¬
ted records refer to a group of small and comparatively insignificant
spiders belonging to the genus Latrodectus, of the family Theridiidae.
The dread “ Malmigniatte” of Corsica and South Europe, the “Kara-
kurte” of southeastern Russia, the “Katipo” of New Zealand the
“Mena-vodi” and “ Vaneoho” of Madagascar, hnd our own Latrodectus
mactans, all belong to this genus, and concerning all of these the most
circumstantial accounts of their venomous nature are given. These
accounts are not mere fantastic stories by uneducated natives but in
many cases are reports from thoroughly trained medical men.

The symptoms produced are general, rather than local. As
summarized by Robert (1901) from a study of twenty-two cases
treated in 1888, in the Kherson (Russia) Government Hospital and
Berislaw (Kherson) District Hospital the typical case, aside from
complications, exhibits the following symptoms. The victim sud¬
denly feels the bite, like the sting of a bee. Swelling of the barely
reddened spot seldom follows. The shooting pains, which quickly
set in, are not manifested at the point of injury but localized at the
joints of the lower limb and in the region of the hip. The severity
of the pain forces the victim to the hospital, in spite of the fact that
they otherwise have a great abhorrence of it. The patient is unable
to reach the hospital afoot, or, at least, not without help, for there is
usually inability to walk. The patient, even if he has ridden, reaches
the hospital covered with cold sweat and continues to perspire for a
considerable period. His expression indicates great suffering. The
respiration may be somewhat dyspnoeic, and a feeling of oppression
in the region of the heart is common. There is great aversion to
solid food, but increasing thirst for milk and tea. Retention of
urine, and constipation occur. Cathartics and, at night, strong

Spiders of the Genus Latrodectus

narcotics are desired. Warm baths give great relief. After three
days, there is marked improvement and usually the patient is dis¬
missed after the fifth. This summary of symptoms agrees well with
other trustworthy records.

It would seem, then, that Riley and Howard (1889), who discussed
a number of accounts in the entomological literature, were fully
justified in their statement that “It must be admitted that certain
spiders of the genus Latrodectus have the power to inflict poisonous
bites, which may (probably exceptionally and depending upon excep¬
tional conditions) bring about the death of a human being.”

And yet, until recently the evidence bearing on the question has
been most conflicting. The eminent arachnologist, Lucas, (1843)
states that he himself, had been repeatedly bitten by the Malmigniatte
without any bad effects. Dr. Marx, in 1890, gave before the Ento¬
mological Society of Washington, an account of a series of experiments
to determine whether the bite of Latrodectus mactans is poisonous or
not. He described the poison glands as remarkably small* and stated
that he had introduced the poison in various ways into guinea-pigs
and rabbits without obtaining any satisfactory results. Obviously,
carefully conducted experiments with the supposed venom were
needed and fortunately they have been carried out in the greatest
detail by Robert (1901).

This investigator pointed out that there were two factors which
might account for the discrepancies in the earlier experiments. In
the first place, the poison of spiders, as of snakes, might be so ex¬
hausted after two or three bites that further bites, following directly,
might be without visible effect. Secondly, the application of the
poison by means of the bite, is exceedingly inexact, since even after
the most careful selection of the point of application, the poison might
in one instance enter a little vein or lymph vessel, and in another case
fail to do so. Besides, there would always remain an incalculable and
very large amount externally, in the nonabsorptive epithelium.
While all of these factors enter into the question of the effect of the
bite in specific instances, they must be as nearly as possible obviated
in considering the question of whether the spiders really secrete a
venom harmful to man.

*This is diametrically opposed to the findings of Bordas (1905) in the case
of the European Latrodectus ij-guttatus, whose glands are “much larger than
those of other spiders.” From a considerable comparative study, we should also
unhesitatingly make this statement regarding the glands of our American species,
L. mactans.

Poisonous Arthropods

Kobert therefore sought to prepare extracts which would contain
the active principles of the poison and which could be injected in
definite quantities directly into the blood of the experimental animal.
For this purpose various parts of the spiders were rubbed up in a mor¬
tar with distilled water, or physiological salt solution, allowed to
stand for an hour, filtered, and then carefully washed, by adding water
drop by drop for twenty-four hours. The filtrate and the wash-
water were then united, well mixed and, if necessary, cleared by cen¬
trifuging or by exposure to cold. The mixture was again filtered,
measured, and used, in part, for injection and, in part, for the deter¬
mination of the organic materials.

Such an extract was prepared from the cephalothoraces of eight
dried specimens of the Russian Latrodectus and three cubic centimeters
of this, containing 4.29 mg. of organic material, were injected into
the jugular vein of a cat weighing 2450 grams. The previously very
active animal was paralyzed and lay in whatever position it was
placed. The sensibility of the skin of the extremities and the rump
was so reduced that there was no reaction from cutting or sticking.
There quickly followed dyspnoea, convulsions, paralysis of the
respiratory muscles and of the heart. I11 twenty-eight minutes the
cat was dead, after having exhibited exactly the symptoms observed
in severe cases of poisoning of man from the bite of this spider.

These experiments were continued on cats, dogs, guinea pigs and
various other animals. Not only extracts from the cephalothorax,
but from other parts of the body, from newly hatched spiders, and
from the eggs were used and all showed a similar virulence. Every
effort was made to avoid sources of error and the experiments, con¬
ducted by such a recognized authority in the field of toxicology, must
be accepted as conclusively showing that this spider and, presumably,
other species of the genus Latrodectus against which the clinical evi¬
dence is quite parallel, possess a poison which paralyzes the heart and
central nervous system, with or without preliminary stimulus of the
motor center. If the quantity of the poison which comes into direct
contact with the blood is large, there may occur haemolysis and
thrombosis of the vessels.

On ihe other hand, check experiments were carried out, using
similar extracts of many common European spiders of the genera
Tegenaria, Drassus, Agelena, Eucharia and Argyroneta, as well as
the Russian tarantula, Lycosa singoriensis. In no other case was the
effect on experimental animals comparable to the Latrodectus extract-

Spiders of the Genus Latrodectus

Robert concludes that in its chemical nature the poison is neither
an alkaloid, nor a glycoside, nor an acid, but a toxalbumen, or poison¬
ous enzyme which is very similar to certain other animal poisons,
notably that of the scorpion.

9 . Latrodectus mactans; (a) female, x 3; ( b ) venter of female; (e) dorsum of male.

After Comstock.

The genus Latrodectus is represented in the United States by at
least two species, L. mactans and L. geometricus. Concerning L.
mactans there are very circumstantial accounts of serious injury and
even death in man*. Latrodectus mactans is coal black, marked with
red or yellow or both. It has eight eyes, which arc dissimilar in

*Dr. E. H. Coleman (Kellogg, 1915) has demonstrated its virulence by a series
of experiments comparable with those of Kobert.

Poisonous Arthropods

color and are distinctly in front of the middle of the thorax, the
lateral eyes of each side widely separate. The tarsi of the fourth
pair of legs has a number of curved setae in a single series. It has on
the ventral side of its abdomen an hour-glass shaped spot. The full-
grown female is about half an inch in length. Its globose abdomen is
usually marked with one or more red spots dorsally along the middle
line. The male is about half as long but has in addition to the dorsal
spots, four pairs of stripes along the sides. Immature females
resemble the male in coloring (fig. 9).

Regarding the distribution of Latrodectus mactans, Comstock
states that: “Although it is essentially a Southern species, it occurs
in Indiana, Ohio, Pennsylvania, New Hampshire, and doubtless other
of the Northern States.” L. geometricus has been reported from
California.

Other Venomous Spiders —While conclusive evidence regarding
the venomous nature of spiders is meager and relates almost wholly
to that of the genus Latrodectus, the group is a large one and we are
not justified in dismissing arbitrarily, all accounts of injury from their
bites. Several species stand out as especially needing more detailed
investigation.

Chiracanthium nutrix is a common European species of the family
Clubionidse, concerning which there is much conflicting testimony.
Among the reports are two by distinguished scientists whose accounts
of personal experiences cannot be ignored. A. Forel allowed a spider
of this species to bite him and not only was the pain extreme, but the
general symptoms were so severe that he had to be helped to his
house. The distinguished arachnologist, Bertkau reports that he,
himself, was bitten and that an extreme, burning pain spread almost
instantaneously over the arm and into the breast. There were slight
chills the same day and throbbing pain at the wound lasted for days.
While this particular species is not found in the United States, there
are two other representatives of the genus and it is possible that they
possess the same properties. We are unaware of any direct experi¬
mental work on the poison.

Epeira diadema, of Europe, belongs to a wholly different group,
that of the orb-weavers, but has long been reputed venomous. Robert
was able to prepare from it an extract whose effects were very similar
to that prepared from Latrodectus, though feebler in its action. Under
ordinary circumstances this spider is unable to pierce the skin of man

Other Venomous Spiders

and though Robert’s results seem conclusive, the spider is little to
be feared.

Phidippus audax ( P. tripunctatus) is one of our largest Attids,
or jumping spiders. The late Dr. O. Lugger describes a case of severe
poisoning from the bite of this spider and though details are lacking,
it is quite possible that this and other large species of the same group,
which stalk their prey, may possess a more active poison than that of
web-building species.

Summary It is clearly established that our common spiders are
not to be feared and that the stories regarding their virulence are

10 . A whip-scorpion (Mastigoproctus giganteus).
Half natural size. After Comstock.

and may even cause death in man

THE PEDIPALPIDA OR

almost wholly without founda¬
tion. On the other hand, the
chances of secondary infection
from the bites of some of the
more powerful species are not
to be ignored.

Probably all species possess
a toxin secreted by the poison
gland, virulent for insects and
other normal prey of the
spiders, but with little or no
effect on man.

There are a very few species,
notably of the genus Latrodectus ,
and possibly including the Euro¬
pean Chiracantkium nutrix and
Epeira diadema, which possess,
in addition, a toxalbumen
derived from the general body
tissue, which is of great virulence
and the higher animals.

WHIP-SCORPIONS

The tailed whip-scorpions, belonging to the family Thelyphonidae,
are represented in the United States by the giant whip-scorpion
Mastigoproctus giganteus (fig. 10), which is common in Florida, Texas
and some other parts of the South. In Florida, it is locally known as
the “grampus” or “mule-killer” and is very greatly feared. There is
no evidence that these fears have any foundation, and Dr. Marx
states that there is neither a poison gland nor a pore in the claw of the
chelicera.

Poisonous Arthropods

THE SC 0 RPI 0 NIDA, OR TRUE SCORPIONS

The true scorpions are widely distributed throughout warm coun¬
tries and everywhere bear an evil reputation. According to Comstock
(1912), about a score of species occur in the Southern United States.
These are comparatively small forms but in the tropics members of
this group may reach a length of seven or eight inches. They are
pre-eminently predaceous forms, which lie hidden during the day and
seek their prey by night.

The scorpions (fig. 11) possess large pedipalpi, terminated by
strongly developed claws, or chelae. They may be distinguished from
all other Arachnids by the fact that the dis¬
tinctly segmented abdomen is divided into a
broad basal region of seven segments and a
terminal, slender, tail-like division of five
distinct segments.

The last segment of the abdomen, or
telson, terminates in a ventrally-directed,
sharp spine, and contains a pair of highly
developed poison glands. These glands open
by two small pores near the tip of the spine.
Most of the species when running carry the
tip of the abdomen bent upward over the
back, and the prey, caught and held by the
pedipalpi, is stung by inserting the spine of
the telson and allowing it to remain for a
time in the wound.

The glands themselves have been studied
in Prionurus citrinus by Wilson (1904).
He found that each gland is covered by a sheet of muscle on its
mesal and dorsal aspects, which may be described as the compressor
muscle. The muscle of each side is inserted by its edge along the
ventral inner surface of the chitinous wall of the telson, close to the
middle line, and by a broader insertion laterally. A layer of fine
connective tissue completely envelops each gland and forms the
basis upon which the secreting cells rest. The secreting epithelium
is columnar; and apparently of three different types of cells.

1. The most numerous have the appearance of mucous cells,
resembling the goblet cells of columnar mucous membranes. The
nucleus, surrounded by a small quantity of protoplasm staining with
hematoxylin, lies close to the base of the cell.

A true scorpion.
Comstock.

After

The True Scorpions

2. Cells present in considerable numbers, the peripheral por¬
tions of which are filled with very numerous fine granules, staining
with acid dyes such as methyl orange.

3. Cells few in number, filled with very large granules, or ir¬
regular masses of a substance staining with hasmatoxylin.

The poison, according to Robert (1893), is a limpid, acid-reacting
fluid, soluble in water but insoluble in absolute alcohol and ether.
There are few data relative to its chemical nature. Wilson (1901)
states that a common Egyptian species, Buthus quinquestriatus, has
a specific gravity of 1.092, and contains 20.3% of solids and 8.4% ash.

The venom of different species appears to differ not only quantita¬
tively but qualitatively. The effects of the bite of the smaller species
of the Southern United States may be painful but there is no satis¬
factory evidence that it is ever fatal. On the other hand, certain
tropical species are exceedingly virulent and cases of death of man
from the bite are common.

In the case of Buthus quinquestriatus, Wilson (1904) found the
symptoms in animals to be hypersecretion, salivation and lachryma-
tion, especially marked, convulsions followed by prolonged mus¬
cular spasm; death from asphyxia. The temperature shows a
slight, rarely considerable, rise. Rapid and considerable increase
of blood-pressure (observed in dogs) is followed by a gradual fall with
slowing of the heart-beat. The coagulability of the blood is not
affected.

An interesting phase of Wilson’s work was the experiments on
desert mammals. The condition under which these animals exist
must frequently bring them in contact with scorpions, and he found
that they possess a degree of immunity to the venom sufficient at
least to protect them from the fatal effects of the sting.

As far as concerns its effect on man, Wilson found that much
depended upon the age. As high as 60 per cent of the cases of
children under five, resulted fatally. Caroroz (1865), states that in a
Mexican state of 15,000 inhabitants, the scorpions were so abundant
and so much feared that the authorities offered a bounty for their
destruction. A result was a large number of fatalities, over two
hundred per year. Most of the victims were children who had
attempted to collect the scorpions.

The treatment usually employed in the case of bites by the more
poisonous forms is similar to that for the bite of venomous snakes.
First, a tight ligature is applied above the wound so as to stop the

Poisonous Arthropods

flow of blood and lymph from that region. The wound is then
freely excised and treated with a strong solution of permanganate
of potash, or with lead and opium lotion.

In recent years there have been many attempts to prepare an
antivenom, or antiserum comparable to what has been used so
effectively in the case of snake bites. The most promising of these
is that of Todd (1909), produced by the immunization of suitable
animals. This antivenom proved capable of neutralizing the venom
when mixed in vitro and also acts both prophylaeticallv and cura-
tively in animals. Employed eurativelv in man, it appears to have
a very marked effect on the intense pain following the sting, and
the evidence so far indicates that its prompt use greatly reduces
the chance of fatal results.

THE SOLPUGIDA, OR SOLPUGLDS

The Solpugida are peculiar spider-like forms which are distin¬
guished from nearh r all other
arachnids by the fact that
they possess no true cephalo-
thorax, the last two leg-bear¬
ing segments being distinct,
resembling those of the abdo¬
men in this respect. The
first pair of legs is not used
in locomotion but seemingly
functions as a second pair of
pedipalpi. Figure 12 illus¬
trates the striking peculiari¬
ties of the group. They are
primarily desert forms and
occur in the warm zones of
all countries. Of the two
hundred or more species,
Comstock lists twelve as
occurring in our fauna.
These occur primarily in the
southwest.

The Solpugida have long
borne a bad reputation and regarding virulence, have been classed
with the scorpions. Among fthe effects of their bites have been

12 . A solpugid (Eremobates cinerea). After Com¬
stock.

Mites and Ticks

described painful swelling, gangrene, loss of speech, cramps, deliri¬
um, unconsciousness and even death. Opposed to the numerous loose
accounts of poisoning, there are a number of careful records by
physicians and zoologists which indicate clearly that the effects are
local and though they may be severe, they show not the slightest
symptom of direct poisoning.

More important in the consideration of the question is the fact
that there are neither poison glands nor pores in the fangs for the
exit of any poisonous secretion. This is the testimony of a number
of prominent zoologists, among whom is Dr. A. Walter, who wrote
to Robert at length on the subject and whose conclusions are pre¬
sented by him.

However, it should be noted that the fangs are very powerful
and are used in such a manner that they may inflict especially severe
wounds. Thus, there may be more opportunity for secondary
infection than is usual in the case of insect wounds.

The treatment of the bite of the Solpugida is, therefore, a matter
of preventing infection. The wound should be allowed to bleed
freely and then washed out with a 113000 solution of corrosive
sublimate, and, if severe, a wet dressing of this should be applied.
If infection takes place, it should be treated in the usual man¬
ner, regardless of its origin.

THE ACARINA, OR MITES AND TICKS

A number of the parasitic Acarina evidently secrete a
specific poison, presumably carried by the saliva, but in most cases
its effect on man is insignificant. There is an abundant literature
dealing with the poisonous effect of the bite of these forms, especially
the ticks, but until recently it has been confused by failure to recog¬
nize that various species may transmit diseases of man, rather than
produce injur}' through direct poisoning. We shall therefore
discuss the Acarina more especially in subsequent chapters, dealing
with parasitism and with disease transmission.

Nevertheless, after the evidence is sifted, there can be no doubt
that the bites of certain ticks may occasionally be followed by a
direct poisoning, which may be either local or general in its effects.
Nuttall (1908) was unable to determine the cause of the toxic effect,
for, in Argas persicus, the species most often implicated, he failed to
get the slightest local or general effect on experimental animals, from
the injection of an emulsion prepared by crushing three of the ticks.

Poisonous Arthropods

It seems clearly established that the bite of certain ticks may
cause a temporary paralysis, or even complete paralysis, involving
the organs of respiration or the heart, and causing death. In 1912,
Dr. I. U. Temple, of Pendleton, Oregon, reported several cases of
what he called “acute ascending paralysis” associated with the occur¬
rence of ticks on the head or the back of the neck. A typical severe
case was that of a six year old child, who had retired in her usual
normal health. The following morning upon arising she was unable
to stand on her feet. She exhibited paralysis extending to the knees,
slight temperature, no pain, sensory nerves normal, motor nerves
completely paralyzed, reflexes absent. The following day the paral¬
ysis had extended to the upper limbs, and before night of the third
day the nerves of the throat (hypoglossal) were affected. The thorax
and larynx were involved, breathing was labored, she was unable
to swallow liquids, phonation was impossible and she could only make
low, gutteral sounds. At this stage, two ticks, fully distended with
blood, Were found over the junction of the spinal column with the
occipital bones in the hollow depression. They were removed by
the application of undiluted creoline. Though the child’s life was
despaired of, by the following morning she was very much improved.
By evening she was able to speak. The paralysis gradually receded,
remaining longest in the feet, and at the end of one week the patient
was able to go home.

There was some doubt as to the exact species of tick implicated
in the cases which Dr. Temple reported, although the evidence
pointed strongly to Dermacentor venustus.* Somewhat later, Hadwen
(1913) reported that “tick paralysis” occurs in British Columbia,
where it affects not only man, but sheep and probably other animals.
It is caused by the bites of Dermacentor venustus and was experi¬
mentally produced in lambs and a dog (Hadwen and Nuttall, 1913).
It is only when the tick begins to engorge or feed rapidly, some days
after it has become attached, that its saliva produces pathogenic
effects.

Ulceration following tick bite is not uncommon. In many of the
instances it is due to the file-like hypostome, with its recurved teeth,
being left in the wound when the tick is forcibly pulled off.

*According to Stiles, the species occurring in the Northwest which is commonly
identified as D. venustus should be called D. andersonii (see footnote, chapter 12).

Centipedes and Millipedes

.Se-o

THE MYRIAPODA, OR CENTIPEDES AND MILLIPEDES

The old class, Myriapoda includes the Diplopoda, or
millipedes, and the Chilopoda, or centipedes. The pres¬
ent tendency is to raise these groups to the rank of
classes.

The Diplopoda

The Diplopoda, or millipedes (fig. 13), are character¬
ized by the presence of two pairs of legs to a segment.
The largest of our local myriapods belong to this group.
They live in moist places, feeding primarily on decay¬
ing vegetable matter, though a few species occasion¬
ally attack growing plants.

The millipedes are inoffensive and harmless. Julus
terrestris, and related species, when irritated pour out
over the entire body a yellowish secretion which escapes
from cutaneous glands. It is
volatile, with a pungent odor,
and Phisalix (1900) has shown
that it is an active poison when
Mter Comstock injected into the blood of experi¬
mental animals. This, how¬
ever, does not entitle
them to be considered
as poisonous arthro¬
pods, in the sense of this
chapter, any more than
the toad can be con¬
sidered poisonous to
man because it secretes
a venom from its cuta¬
neous glands.

The Chilopoda

The Chilopoda, or

centipedes (fig. 14), un¬
like the millipedes, are
predaceous forms, and
possess well developed
poison glands for kill¬
ing their prey. These

14. Two common centipedes.

(a) Lithobius forficatus. (6) Scutigera forceps. Natural

After Comstock.

size; after Howard.

Poisonous Arthropods

15. Mandible of
Scolopendra
cingulata
showing
venom
gland. After
Dubosq.

glands are at the base of the first pair of legs (fig. 15), which are
bent forward so as to be used in holding their prey. The legs
terminate in a powerful claw, at the tip of which is the
outlet of the poison glands.

The poison is a limpid, homogeneous, slightly acid
fluid, which precipitates in distilled water. Briot (1904)
extracted it from the glands of Scolopendra morsitans , a
species common in central France, and found that it was
actively venomous for the ordinary experimental ani¬
mals. A rabbit of two kilograms weight received an
injection of three cubic centimeters in the vein of the ear
and died in a minute. A white rat, weighing forty-eight
grams, received one and a half cubic centimeters in the
hind leg. There was an almost immediate paralysis of
the leg and marked necrosis of the tissues.

As for the effect on man, there is little foundation for the fear
with which centipedes are regarded. Our native species produce,
at most, local symptoms,—sometimes severe local pain and swell¬
ing,-—but there is no authentic record of fatal results. In the tropics,
some of the species attain a large size, Scolopendra gigantea reaching
a length of nearly a foot. These forms are justly feared, and there
is good evidence that death sometimes, though rarely, results from
their bite.

One of the most careful accounts of death from the sting of the
scorpion is that of Linnell, (1914), which relates to a comparatively
small Malayan species, unfortunately undetermined. The patient,
a coolie, aged twenty, was admitted to a hospital after having been
stung two days previously on the left heel. For cure, the other
coolies had made him eat the head of the scorpion. On admission,
the patient complained of “things creeping all over the body”.
Temp. 102.8°. On the fourth day he had paralysis of the legs, and
on the fifth day motor paralysis to the umbilicus, sensation being
unaltered. On the sixth day there was retention of the urine and
on the ninth day (first test after third day) sugar was present. On
the thirteenth day the patient became comatose, but could be
roused to eat and drink. The temperature on the following day fell
below 95° and the patient was still comatose. Death fifteenth day.

Examination of the spinal (lumbar) cord showed acute dissemi¬
nated myelitis. In one part there was an acute destruction of the
anterior horn and an infiltration of round cells. In another portion

Hexapoda, or True Insects

Clarke’s column had been destroyed. The perivascular sheaths
were crowded with small round cells and the meninges were con¬
gested. Some of the cells of the anterior horn were swollen and the
nuclei eccentric; chromatolysis had occurred in many of them.

As for treatment, Castellani and Chalmers (1910), recommend
bathing the part well with a solution of ammonia (one in five, or one
in ten). After bathing, apply a dressing of the same alkali or, if
there is much swelling and redness, an ice-bag. If necessary, hypo¬
dermic injections of morphine may be given to relieve the pain.
At a later period fomentations may be required to reduce the local
inflammation.

THE HEXAPODA OR TRUE INSECTS

There are a number of Hexapoda, or true insects, which are, in
one way or another, poisonous to man. These belong primarily
to the orders Hemiptera, or true bugs; Lepidoptera, or butterflies
and moths (larval forms); Diptera, or flies; Coleoptera, or beetles;
and Hymenoptera, or ants, bees, and wasps. There are various ways
in which they may be poisonous.

1. Piercing or biting forms may inject an irritating or poisonous
saliva into the wound caused by their mouth-parts.

2. Stinging forms may inject a poison, from glands at the caudal
end of the abdomen, into wounds produced by a specially modified
ovipositer, the sting.

3. Nettling properties may be possessed by the hairs of the insect.

4. Vescicating, or poisonous blood plasma , or body fluids are
known to exist in a large number of species and may, under excep¬
tional circumstances, affect man.

For convenience of discussion, we shall consider poisonous insects
under these various headings. In this, as in the preceding discussion,
no attempt will be made to give an exhaustive list of the poisonous
forms. Typical instances will be selected and these will be chosen
largely from North American species.

PIERCING OR BITING INSECTS POISONOUS TO MAN
Hemiptera

Several families of the true bugs include forms which, while
normally inoffensive, are capable of inflicting painful wounds on man.
In these, as in all of the Hemiptera, the mouth-parts are modified

Poisonous Arthropods

to form an organ for piercing and
sucking. This is well shown by the
accompanying illustration (fig. 16).

Theupper lip, or labrum, ismuch
reduced and immovable, the lower
lip, or labium, is elongated to form
a jointed sheath, within which the
lance-like mandibles and maxillae
are enclosed. The mandibles are
more or less deeply serrate, depend¬
ing on the species concerned.

The poison is elaborated by the salivary glands, excepting, possi¬
bly, in Belostoma where Locy is inclined to believe that it is secreted
by the maxillary glands. The salivary glands
of the Hemiptera have been the subject of
much study but the most recent, eomprehen-
sivepvork has been done by Bugnion and Popoff,

(1908 and 1910) to whose text the reader is
referred for details.

The Hemiptera have two
pairs of salivary glands: the
primary gland, of which the
efferent duct leads to the
salivary syringe, and the
accessory gland, of which the
very long and flexuous duct
empties into the primary duct
at its point of insertion.

Thus, when one observes the
isolated primary gland it appears as though it
had efferent ducts inserted at the same point. In
Nepa and the Fulgoridce there are two accessory
glands and therefore apparently three ducts
at the same point on the primary gland. The
ensemble differs greatly in appearance in different
species but we shall show here Bugnion and
Popoff’s figure of the apparatus of Notonecta
maculata, a species capable of inflicting a painful

17.

Salivary glands of
Notonecta maculata.
After Bugnion and
Popoff.

18. Pharyngeal syrinve or
salivary pump of Ful-

l“";a*Pop T’ bite on man (fig. i 7 ).

Hemiptem, or True Bugs

Accessory to the salivary apparatus there is on the ventral side
of the head, underneath the pharynx, a peculiar organ which the

19. Heteroptera, (a) Melanolestes picipes; (6) Notonecta undulata; (c.d) Aradus robustus
(c) adult, (d) nymph, much enlarged; (e) Arilus cristatus; (/) Belostoma americana;
J(g) Nabis (Coriscus) subcoleoptratus, enlarged; ( h ) Cimex lectularius. (») Oeciacus
vicarius, much enlarged; (/) Lyctocoris fitchii, much enlarged After Lugger.

Germans have called the “ Wanzenspritze,” or syringe. The ac¬
companying figure of the structure in Fulgora maculata (fig. 18) shows
its relation to the ducts of the salivary glands and to the beak. It is

3 °

Poisonous Arthropods

made up of a dilatation forming the body of the pump, in which there
is a chitinous piston. Attached to the piston is a strong retractor
muscle. The function of the salivary pump is to suck up the saliva
from the salivary ducts and to force it out through the beak.

Of the Hemiptera reported as attacking man, we shall consider
briefly the forms most frequently noted.

The Notonectidae, or back swimmers, (fig. igb) are small, aquatic
bugs that differ from all others in that they always swim on their
backs. They are predaceous, feeding on insects and other small
forms. When handled carelessly they are able to inflict a painful
bite, which is sometimes as severe as the sting of a bee. In fact,
they are known in Germany as “ Wasserbienen.”

The Belostomatidee, or giant water bugs, (fig. 19/) include the largest
living Hemiptera. They are attracted to lights and on account of the
large numbers which swarm about the electric street lamps in some
localities they have received the popular name “electric light bugs.’’
Our largest representatives in the northern United States belong to
the two genera Belostoma and Banacus, distinguished from each
other by the fact that Belostoma has a groove on the under side of
the femur of the front leg, for the reception of the tibia.

The salivary glands of Belostoma were figured by Leidy (1847)
and later were studied in more detail by Locy (1884). There are
two pairs of the glands, those of one pair being long and extending
back as far as the beginning of the abdomen, while the others are
about one-fourth as long. They lie on either side of the oesophagus.
On each side of the oesophagus there is a slender tube with a
sigmoid swelling which may serve as a poison reservoir. In addi¬
tion to this salivary system, there is a pair of very prominent glands
on the ventral side of the head, opening just above the base of the
beak. These Locy has called the “cephalic glands” and he suggests
that they are the source of the poison. They are the homologues
of the maxillary glands described for other Hemiptera, and it is by
no means clear that they are concerned with the production of
venom. It seems more probable that in Belostoma, as in other
Hemiptera, it is produced by the salivary glands, though the question
is an open one.

The Belostomatidae feed not only on insects, but on small frogs,
fish, salamanders and the like. Mathcson (1907) has recorded the
killing of a good-sized bird by Belostoma americana. A woodpecker,

Hemiptera , or True Bugs

3 1

Reduvius (Opsiccetus)
personatus. (x2).

cause

shooting pains that
may extend through¬
out the arm and that
they may be felt for several days.

Relief from the pain may be obtained by
the use of dilute ammonia, or a menthol
ointment. In the not uncommon case of
secondary infection the usual treatment for
that should be adopted.

The Reduviidas, or assassin-bugs are cap¬
able of inflicting very painful wounds, as

most collect¬

or flicker, was heard to utter cries of distress,
and fluttered and fell from a tree. On exam¬
ination it was found that a bug of this species
had inserted its beak into the back part of
the skull and was apparently busily engaged
in sucking the blood or brains of the bird.
Various species of Belostoma have been cited
as causing painful bites in man. We can
testify from personal experience that the bite
of Belostoma americana may almost immedi¬
ately cause severe,

21.

(a) Reduvius personatus,
nymph.

Photograph by M. V. S.

(b) Reduvius personatus, adult (x2)
Photograph by M. V. S.

ors of Hemip¬
tera know to
their sorrow.

Some species are frequently to be
found in houses and outhouses and
Dr. Howard suggests that many of
the stories of painful spider bites
relate to the attack of these forms.

An interesting psychological study
was afforded in the summer of 1899,
by the “kissing-bug” scare which
swept over the country. It was
reported in the daily papers that a
new and deadly bug had made its
appearance, which had the unpleasant
habit of choosing the lips or cheeks

Poisonous Arthropods

for its point of attack on man. So widespread were the stories
regarding this supposedly new insect that station entomologists all

over the country began to receive sus¬
pected specimens for identification. At
Cornell there were received, among
others, specimens of stone-flies, may¬
flies and even small moths, with in¬
quiries as to whether they were “kiss-
ing-bugs.”

Dr. L. 0 . Howard has shown that the
scare had its origin in newspaper reports
of some instances of bites by either
Melanolestes picipes (fig. 19a) or Opsi-
coetes personatus (fig. 20), in the vicinity
of Washington, D. C. He then discusses
in considerable detail the more promi-
22 ' 1 Howa U rd blguttatus ’ (x2) ' Aftcr nen ^ the Reduviidse which, with

greater or less frequency pierce the skin
of human beings. These are Opsicoetes personatus, Melanolestes
picipes, Coriscus suhcoleoptratus (fig. i9g), Rasahus tlioracicus.
Rasahus biguttatus (fig. 22), Conorhinus sanguisugus (fig. 71), and C.
abdominalis (fig. 23).

One of the most interesting of these species is Reduvius personatus,
(= Opsiccetus personatus) , which is popularly known as the ‘ ‘ masked
bed-bug hunter.” It owes this
name to the fact that the imma¬
ture nymphs (fig. 21) have their
bodies and legs completely covered
by dust and lint, and that they
are supposed to prey upon bed¬
bugs. LeConte is quoted by How¬
ard as stating that * * This species is
remarkable for the intense pain
caused by its bite. I do not know
whether it ever willingly plunges
its rostrum into any person, but
when caught, or unskilfully handled
it always stings. In this case the
pain is almost equal to the bite of a snake, and the swelling and
irritation which result from it will sometimes last for a week.”

Diptera

A species which very commonly attacks man is Conorhinus
sanguisugus , the so-called “big bed-bug” of the south and southern
United States. It is frequently found in houses and is known to
inflict an exceedingly painful bite. As in the case of a number of
other predaceous Hemiptera, the salivary glands of these forms are
highly developed. The effect of the bite on their prey and, as Marlatt
has pointed out, the constant and uniform character of the symptoms
in nearly all cases of bites in man, clearly indicate that their saliva
contains a specific substance. No satisfactory studies of the secre¬
tions have been made. On the other hand, Dr. Howard is doubt¬
less right in maintaining that the very serious results which some¬
times follow the bite are due to the introduction of extraneous poison
germs. This is borne out by the symptoms of most of the cases
cited in literature and also by the fact that treatment with corrosive
sublimate, locally applied to the wound, has yielded favorable results.

Other Hemiptera Reported as Poisonous to Man —A large number
of other Hemiptera have been reported as attacking man. Of these,
there are several species of Lygaeidas, Coreidae, and Capsidas. Of the
latter, Lygns pratensis, the tarnished plant-bug, is reported by
Professor Crosby as sucking blood. Orthotylus flavosparsus is another
Capsid which has been implicated. Empoasca malt and Platymetopius
acutus of the Jassidas have also been reported as having similar
habits.

Whenever the periodical cicada or “seventeen-year locust” be¬
comes abundant, the newspapers contain accounts of serious results
from its bites. The senior author has made scores of attempts to
induce this species to bite and only once successfully. At that
time the bite was in no wise more severe than a pin-prick. A stu¬
dent in our department reports a similar experience. There is no
case on record which bears evidence of being worthy of any credence,
whatsoever.

Under the heading of poisonous Hemiptera we might consider the
bed-bugs and the lice. These will be discussed later, as parasites
and as carriers of disease, and therefore need only be mentioned here.

DIPTERA

Several species of blood-sucking Diptera undoubtedly secrete a
saliva possessing poisonous properties. Chief among these are the
Culicidae, or mosquitoes, and the Simuliidas, or black-flies. As we
shall consider these forms in detail under the heading of parasitic

Poisonous Arthropods

species and insects transmitting disease, we shall discuss here only
the poison of the mosquitoes.

It is well known that mosquitoes, when they bite, inject into the
wound a minute quantity of poison. The effect of this varies accord¬
ing to the species of mosquito and also depends very much on the
susceptibility of the individual. Soon after the bite a sensation of
itching is noticed and often a wheal, or eminence, is produced on the
skin, which may increase to a considerable swelling. The scratching
which is induced may cause a secondary infection and thus lead to
serious results. Some people seem to acquire an immunity against
the poison.

The purpose of this irritating fluid may be, as Reaumur suggested,
to prevent the coagulation of the blood and thus not only to cause
it to flow freely when the insect bites but to prevent its rapid coagula¬
tion in the stomach. Obviously, it is not developed as a protective
fluid, and its presence subjects the group to the additional handicap
of the vengeance of man.

As to the origin of the poison, there has been little question,
until recent years, that it was a secretion from the salivary glands.

Macloskie (1888) showed
that each gland is sub¬
divided into three lobes,
the middle of which differs
from the others in having
evenly granulated contents
and staining more deeply

24. Diagram of a longitudinal section of a mosquito.

than the others (fig. 24). This middle lobe he regarded as the source
of the poison. Brack, (1911), by the use of water, glycerine, chloro¬
form, and other fluids, extracted from the bodies of a large number
of mosquitoes a toxine which he calls culicin. This he assumes
comes from the salivary glands. Animal experimentation showed
that this extract possessed hemolytic powers. Inoculated into the
experimenter’s own skin it produced lesions which behaved exactly
as do those of mosquito bites.

Similarly, most writers on the subject have concurred with the
view that the salivary glands are the source of the poison. How¬
ever, recent work, especially that of Nuttall and Shipley (1903),
and Schaudinn (1904), has shown that the evidence is by no means
conclusive. Nuttall dissected out six sets (thirty-six acini) of glands
from freshly killed Culex pipiens and placed them in a drop of salt

Diptera

solution. The drop was allowed to dry, it being thought that the
salt crystals would facilitate the grinding up of the glands with the
end of a small glass rod, this being done under microscopic control.
After grinding up, a small drop of water was added of the size of the
original drop of saline, and an equal volume of human blood taken
from the clean finger-tip was quickly mixed therewith, and the whole
drawn up into a capillary tube. Clotting was not prevented and no
hemolysis occurred. Salivary gland emulsion added to a dilute
suspension of corpuscles did not lead to hemolysis. This experi¬
ment was repeated a number of times, with slight modification, but
with similar results. The data obtained from the series “do not
support the hypothesis that the salivary glands, at any rate in Culex
pipiens, contain a substance which prevents coagulation.”

Much more detailed, and the more important experiments made
along this line, are those of Schaudinn (1904). The results of these
experiments w^ere published in connection with a technical paper
on the alternation of generations and of hosts in Trypanosoma and
Spirochoeta, and for this reason seem to have largely escaped the notice
of entomologists. They are so suggestive that w r e shall refer to them
in some detail.

Schaudinn observed that the three oesophageal diverticula (com¬
monly, but incorrectly, knowm as the “sucking stomach”) (fig. 24)
usually contain large bubbles of gas and in addition, he always found
yeast cells. On the ground of numerous observations, Schaudinn
was convinced that these yeast plants are normal and constant
commensals of the insect. He regarded them as the cause of the gas
bubbles to be found in diverticula. It was found that as the insect
fed, from time to time the abdomen underwent convulsive contrac¬
tions which resulted in the emptying of the oesophageal diverticula and
the salivary glands through blood pressure.

In order to test the supposed toxic action of the salivary glands,
Schaudinn repeatedly introduced them under his skin and that of
his assistant, in a drop of salt solution, and never obtained a sugges¬
tion of the irritation following a bite of the insect, even though the
glands were carefully rubbed to fragments after their implantation.
Like Nuttall, he failed to get satisfactory evidence that the secre¬
tion of the salivary glands retarded coagulation of the blood.

He then carefully removed the oesophageal diverticula with their
content of yeast and introduced them into an opening in the skin
of the hand. Within a few seconds there was noticeable the charac-

Poisonous Arthropods

teristic itching irritation of the mosquito bite; and in a short time
there appeared reddening and typical swelling. This was usually
much more severe than after the usual mosquito bite, and the swell¬
ing persisted and itched longer. This was because by the ordinary
bite of the mosquito most of the yeast cells are again sucked up,
while in these experiments they remained in the wound. These
experiments were repeated a number of times on himself, his assistant
and others, and always with the same result. From them Schaudinn
decided that the poisonous action of the mosquito bite is caused by
an enzyme from a commensal fungus. These conclusions have not,
as yet, been satisfactorily tested.

Relief from the effect of the mosquito bite may be obtained by
bathing the swellings with weak ammonia or, according to Howard,
by using moist soap. The latter is to be rubbed gently on the punc¬
ture and is said to speedily allay the irritation. Howard also quotes
from the Journal of Tropical Medicine and Hygiene to the effect that
a few drops of a solution of thirty to forty grains of iodine to an ounce
of saponated petroleum rubbed into the mosquito bite, or wasp sting,
allay the pain instantaneously.

Methods of mosquito control will be discussed later, in consider¬
ing these insects as parasites and as carriers of disease.

STINGING INSECTS

The stinging insects all belong to the order Hymenoptera. In a
number of families of this group the ovipositor is modified to form a
sting and is connected with poison-secreting glands. We shall
consider the apparatus of the honey-bee and then make briefer refer¬
ence to that of other forms.

Apis mellifica, the honey bee —The sting of the worker honey¬
bee is situated within a so-called sting chamber at the end of the
abdomen. This chamber is produced by the infolding of the greatly
reduced and modified eighth, ninth and tenth abdominal segments
into the seventh.* From it the dart-like sting can be quickly ex-
serted.

The sting (fig. 25) is made up of a central shaft, ventro-laterad of
which are the paired lancets, or darts, which are provided with sharp,
recurved teeth. Still further laterad lie the paired whitish, finger-

*It should be remembered that in all the higher Hymenoptera the first ab¬
dominal segment is fused with the thorax and that what is apparently the sixth
segment is, in reality, the seventh.

Stinging Insects

like sting palpi. Comparative morphological as well as embryologi-
cal studies have clearly established that these three parts corres¬
pond to the three pairs of
gonopophyses of the ovipositor
of more generalized insects.

An examination of the inter¬
nal structures (fig. 26) reveals
two distinct types of poison
glands, the acid-secreting and
the alkaline-secreting glands,

25. Sting of a honey bee. Psn Sc, base of acid
and a prominent poison reser- poison gland; B Cl. alkaline poison gland;

. T , I*.* ,1 • Stn Pip, sting palpi; Sh B, bulb of sting;

VOir. in addition, there IS a Sh a, basal arm; Let, lancets or darts; Sh s,

,, . . shaft of sting. Modified from Snodgrass.

small pair of accessory struct¬
ures which have been called lubricating glands, on account of the
supposed function of their product. The acid-secreting gland empties
into the distal end of the poison reservoir which in turn pours the
secretion into the muscular bulb-like enlargement at the base of the
shaft. The alkaline secreting gland empties into the bulb ventrad
of the narrow neck of the reservoir.

The poison is usually referred to as formic acid. That it is not so
easily explained has been repeatedly shown and is evidenced by the
presence of the two types of glands. Carlet maintains that the pro¬
duct of either gland is in itself innocent,
—it is only when they are combined that
the toxic properties appear.

The most detailed study of the poison
of the honey-bee is that of Josef Langer
(1897), who in the course of his work used
some 25,000 bees. Various methods of
obtaining the active poison for experi¬
mental purposes were used. For obtaining
the pure secretion, bees were held in the
fingers and compressed until the sting was
exserted, when a clear drop of the poison
was visible at its tip. This was then taken
up in a capillary tube or dilute solutions
bee. Modified from Snod- obtained by dipping the tip of the sting into
a definite amount of distilled water.

An aqueous solution of the poison was more readily obtained by
pulling out the sting and poison sacs by means of forceps, and grinding

Poisonous Arthropods

them up in water. The somewhat clouded fluid was then filtered
one or more times. For obtaining still greater quantities, advantage
was taken of the fact that while alcohol coagulates the poison, the
active principle remains soluble in water. Hence the stings with
the annexed glands where collected in 96 per cent alcohol, after
filtering off of the alcohol were dried at 40° C., then rubbed to a fine
powder and this was repeatedly extracted with water. Through
filtering of this aqueous extract there was obtained a yellowish-
brown fluid which produced the typical reactions, according to con¬
centration of the poison.

The freshly expelled drop of poison is limpid, of distinct acid
reaction, tastes bitter and has a delicate aromatic odor. On evapora¬
tion, it leaves a sticky residue, which at 100 degrees becomes fissured,
and suggests dried gum arabic. The poison is readily soluble in
water and possesses a specific gravity of 1.1313. On drying at room
temperature, it leaves a residue of 30 per cent, which has not lost in
poisonous action or in solubility. In spite of extended experiments,
Langer was unable to determine the nature of the active principle.
He showed that it was not, as had been supposed, an albuminous
body, but rather an organic base.

The pure poison, or the two per cent aqueous solution, placed on
the uninjured skin showed absolutely no irritating effect, though it
produced a marked reaction on the mucus membrane of the nose or
eye. A single drop of one-tenth per cent aqueous solution of the
poison brought about a typical irritation in the conjunctiva of the
rabbit’s eye. On the other hand, the application of a drop of the
poison, or its solution, to the slightest break in the skin, or by means
of a needle piercing the skin, produced typical effects. There is pro¬
duced a local necrosis, in the neighborhood of which there is infiltra¬
tion of lymphocytes, oedema, and hyperaemia.

The effect of the sting on man (fig. 27) is usually transitory but
there are some individuals who are made sick for hours, by a single
sting. Much depends, too, on the place struck. It is a common
experience that an angry bee will attempt to reach the eye of its
victim and a sting on the lid may result in severe and prolonged
swelling. In the case of a man stung on the cheek, Legiehn observed
complete aphonia and a breaking out of red blotches all over the
body. A sting on the tongue has been known to cause such collateral
oedema as to endanger life through suffocation. Cases of death of
man from the attacks of bees are rare but are not unknown. Such

Stinging Insects

results are usually from a number of stings but, rarely, death has
been known to follow a single sting, entering a blood vessel of a
particularly susceptible individual.

It is clearly established that partial immunity from the effects
of the poison may be acquired. By repeated injections of the venom,
mice have been rendered capable of bearing doses that certainly
would have killed them at first. It is a well-knowm fact that most
bee-keepers become gradually hardened to the stings, so that the
irritation and the swelling become less and less. Some individuals

Effect of bee stings. After Root.

have found this immunity a temporary one, to be reacquired each
season. A striking case of acquired immunity is related by the
Roots in their “ABC and X Y Z of Bee Culture.” The evidence
in the case is so clear that it should be made more widely available
and hence we quote it here.

A young man who was determined to become a bee-keeper, was so
susceptible to the poison that he was most seriously affected by a
single sting, his body breaking out with red blotches, breathing grow¬
ing difficult, and his heart action being painfully accelerated. “We
finally suggested taking a live bee and pressing it on the back of his
hand until it merely pierced his skin with the sting, then immediately
brushing off both bee and sting. This was done and since no serious
effect followed, it was repeated inside of four or five days. This
was continued for some three or four weeks, when the patient began to
have a sort of itching sensation all over his body. The hypodermic

Poisonous Arthropods

injections of bee-sting poison were then discontinued. At the end
of a month they were repeated at intervals of four or five days.
Again, after two or three weeks the itching sensation came on, but
it was less pronounced. The patient was given a rest of about a
month, when the doses were repeated as before.” By this course
of treatment the young man became so thoroughly immunized that
neither unpleasant results nor swelling followed the attacks of the
insects and he is able to handle bees with the same freedom that any
experienced bee-keeper does.

In an interesting article in the Entomological News for November,
1914, J. H. Lovell calls attention to the fact that “There has been a
widespread belief among apiarists that a beekeeper will receive more
stings when dressed in black than when wearing white clothing.
A large amount of evidence has been published in the various bee
journals showing beyond question that honey-bees under certain
conditions discriminate against black. A few instances may be
cited in illustration. Of a flock of twelve chickens running in a bee-
yard seven black ones were stung to death, while five light colored
ones escaped uninjured. A white dog ran among the bee-hives
without attracting much attention, while at the same time a black
dog was furiously assailed by the bees. Mr. J. D. Byer, a prominent
Canadian beekeeper, relates that a black and white cow, tethered
about forty feet from an apiary, was one afternoon attacked and
badly stung by bees. On examination it was found that the black
spots had five or six stings to one on the white. All noticed this fact,
although no one was able to offer any explanation. A white horse
is in much less danger of being stung, when driven near an apiary,
than a black one. It has, indeed, been observed repeatedly that
domestic animals of all kinds, if wholly or partially black, are much
more liable to be attacked by bees, if they wander among the hives,
than those which are entirely white.

In order to test the matter experimentally, the following series
of experiments was performed. In the language of the investi¬
gator :

“On a clear, warm day in August I dressed wholly in white with
the exception of a black veil. Midway on the sleeve of my right arm
there was sewed a band of black cloth ten inches unde. I then
entered the bee-yard and, removing the cover from one of the hives,
lifted a piece of comb with both hands and gently shook it. Instantly
many of the bees flew to the black band, which they continued to

Stinging Insects

attack as long as they were disturbed. Not a single bee attempted
to sting the left sleeve, which was of course entirely white, and. very
few even alighted upon it.”

‘‘This experiment was repeated a second, third and fourth time;
in each instance with similar results. I estimated the number of bees
on the band of black cloth at various moments was from thirty to
forty; it was evident from their behavior that they were extremely
irritable. To the left white sleeve and other portions of my clothing
they paid very little attention; but the black veil was very frequently
attacked.”

‘‘A few days later the experiments were repeated, but the band of
black cloth, ten inches wide, was sewed around my left arm instead
of around the right arm as before. When the bees were disturbed,
after the hive cover had been removed, they fiercely attacked the
band of black cloth as in the previous experiences; but the right white
sleeve and the white suit were scarcely noticed. At one time a part
of the black cloth was almost literally covered with furiously stinging
bees, and the black veil was assailed by hundreds. The bees behaved
in a similar manner when a second hive on the opposite side of the
apiary was opened.”

‘ ‘A white veil which had been procured for this purpose, was next
substituted for the black veil. The result was most surprising,
for, whereas in the previous experiments hundreds of bees had
attacked the black veil, so few flew against the white veil as to cause
me no inconvenience. Undoubtedly beekeepers will find it greatly
to their advantage to wear white clothing when working among their
colonies of bees and manipulating the frames of the hives.”

When a honey-bee stings, the tip of the abdomen, with the entire
sting apparatus, is torn off and remains in the wound. Here the
muscles continue to contract, for some minutes, forcing the barbs
deeper and deeper into the skin, and forcing out additional poison
from the reservoir.

Treatment, therefore, first consists in removing the sting without
squeezing out additional poison. This is accomplished by lifting
and scraping it out with a knife-blade or the fingernail instead of
grasping and pulling it out. Local application of alkalines, such as
weak ammonia, are often recommended on the assumption that the
poison is an acid to be neutralized on this manner, but these are of
little or no avail. They should certainly not be rubbed in, as that
would only accelerate the absorption of the poison. The use of

Poisonous Arthropods

cloths wrung out in hot water and applied as hot as can be borne,
affords much relief in the case of severe stings. The application of
wet clay, or of the end of a freshly cut potato is sometimes helpful.

In extreme cases, where there is great susceptibility, or where
there may have been many stings, a physician should be called. He
may find strychnine injections or other treatment necessary, if
general symptoms develop.

Other Stinging Forms—Of the five thousand, or more, species
of bees, most possess a sting and poison apparatus and some of the
larger forms are capable of inflicting a much more painful sting than

that of the common honey-bee. In fact, some, like the bumble bees,
possess the advantage that they do not lose the sting from once using
it, but are capable of driving it in repeatedly. In the tropics there
are found many species of stingless bees but these arc noted for their
united efforts to drive away intruders by biting. Certain species
possess a very irritating saliva which they inject into the wounds.

The ants are not ordinarily regarded as worthy of consideration
under the heading of “stinging insects’’ but as a matter of fact,
most of them possess well developed stings and some of them, especi¬
ally in the tropics, are very justly feared. Even those which lack
the sting possess well-developed poison glands and the parts of the
entire stinging apparatus, in so far as it is developed in the various,
species, may readily be homologized with those of the honey-bee.

Stinging Insects

The ants lacking a sting are those of the subfamily Camponotinae,
which includes the largest of our local species. It is an interesting
fact that some of these species possess the largest poison glands and
reservoir (fig. 28) and it is found that when they attack an enemy
they bring the tip of the abdomen forward and spray the poison in
such a way that it is introduced into the wound made by the powerful
mandibles.

More feared than any of the other Hymenoptera are the hornets
and wasps. Of these there are many species, some of which attain

29. A harmless, but much feared larva, the "tomato worm.”
Natural size. Photograph by M. V. S.

a large size and are truly formidable. Phisalix (1897), has made a
study of the venom of the common hornet and finds that, like the
poison of the honey-bee, it is neither an albuminoid nor an alkaloid.
Its toxic properties are destroyed at 120° C. Phisalix also says that
the venom is soluble in alcohol. If this be true, it differs in this
respect from that of the bee. An interesting phase of the w r ork of
Phisalix is that several of her experiments go to show that the venom
of hornets acts as a vaccine against that of vipers.

NETTLING INSECTS

So far, we have considered insects which possess poison glands
connected with the mouth-parts or a special sting and which actively

Poisonous Arthropods

inject their poison into man. There remain to be considered those
insects which possess poisonous hairs or body fluids which, under
favorable circumstances, may act as poisons. To the first of these
belong primarily the larvae of certain Lepidoptera.

LEPIDOPTERA

When we consider the reputedly poisonous larvae of moths and
butterflies, one of the first things to impress us is that we cannot

30. Another innocent but much maligned caterpillar, the larva of the Regal moth.
. Photograph by M. V. S.

judge by mere appearance. Various species of Sphingid, or hawk-
moth larvae, bear at the end of the body a chitinous horn, which is
often referred to as a “sting” and regarded as capable of inflicting
dangerous wounds. It would seem unnecessary to refer to this
absurd belief if it were not that each summer the newspapers con¬
tain supposed accounts of injury from the “tomato worm” (fig. 29)
and others of this group. The grotesque, spiny larva (fig. 30) of
one of our largest moths, Citheronia regalis is much feared though
perfectly harmless, and similar instances could be multiplied.

But if the larva; are often misjudged on account of their ferocious
appearance, the reverse may be true. A group of most innocent
looking and attractive caterpillars is that of the flannel-moth larvae,

Nettling Insects

of which Lagoa crispata may be taken as an example. Its larva
(fig. 31) has a very short and thick body, which is fleshy and com-

31. The flinnel moth (Lagoa crispata). (a) Poisonous larva.

31. ( b ) Adult. Enlarged. Photographs by M. V. S.

pletely covered and hidden by long silken hairs of a tawny or brown
color, giving a convex form to the upper side. Interspersed among

Poisonous Arthropods

these long hairs are numer¬
ous short spines connected
with underlying hvpoder-
mal poison glands. These
hairs are capable of pro¬
ducing a marked nettling
effect when they come in
contact with the skin.
This species is found in
our Atlantic and Southern
States. Satisfactory
studies of its poisonous
hairs and their glands have
not yet been made.

Sihine stimulea ( Em -
pretia stimulea), or the
saddle-back caterpillar
(fig. 32), is another which possesses nettling hairs. This species
belongs to the group of Eucleidae, or slug caterpillars. It can be
readily recognized
by its flattened
form, lateral, brist¬
ling spines and by
the large green
patch on the back
resembling a
saddle-cloth, while
the saddle is repre¬
sented by an oval,
purplish-brown
spot. The small
spines are veno¬
mous and affect
some persons very
painfully. The
larva feeds on the
leaves of a large
variety of forest
trees and also on
cherry, plum, and

; ; V’. ■ :v. ___ s _ 5 __

32 The poisonous saddle back caterpillar. Empretia
(Sibine) stimulea. Photograph by M. V. S.

33a. Io moth larvae on willow. Photograph by M.V. S.

Nettling Insects 47

even corn leaves. It is to be found throughout the Eastern and
Southern United States.

Automeris io is the best known of the nettling caterpillars. It is
the larva of the Io moth, one of the Satumiidae. The mature eater-

336. Io moth. Full grown larva. Photograph by M. V. S.

33c. Io moth. Adult. Photograph by M. V. S.

pillar, (fig. 33), which reaches a length of two and one-half inches, is
of a beautiful pale green with sublateral stripes of cream and red color
and a few black spines among the green ones. The green radiating
spines give the body a mossy appearance. They are tipped with a

Poisonous Arthropods

slender chitinous hair whose tip is readily broken off in the skin and
whose poisonous content causes great irritation. Some individuals
are very susceptible to the poison, while others are able to handle
the larvae freely without any discomfort. The larvae feed on a wide
range of food plants. They are most commonly encountered on
coni and on willow, because of the opportunities for coming in contact
with them.

The larvae of the brown-tail moth (Euproctis chrysorrlioea,) (fig.
35 and 36), where they occur in this country, are, on account of their
great numbers, the most serious of all poisonous caterpillars. It is

35. Larva of brown-tail moth. (Natural size). Photograph by M. V. S.

not necessary here, to go into details regarding the introduction of
this species from Europe into the New England States. This is all
available in the literature from the United States Bureau of Entomol¬
ogy and from that of the various states which are fighting the species.
Suffice to say, there is every prospect that the pest will continue to
spread throughout the Eastern United States and Canada and that
wherever it goes it will prove a direct pest to man as well as to his
plants.

Very soon after the introduction of the species there occurred in
the region where it had gained a foothold, a mysterious dermatitis of
man. The breaking out which usually occurred on the neck or other
exposed part of the body was always accompanied by an intense

Nettling Insects

itching. It was soon found that this dermatitis was caused by certain
short, barbed hairs of the brown-tail caterpillars and that not only the
caterpillars but their cocoons and even the adult female moths might
harbor these nettling hairs and thus give rise to the irritation. In
many cases the hairs were wafted to clothing on the line and when this
was worn it might cause the same trouble. Still worse, it was found
that very serious internal injury was often caused by breathing or
swallowing the poisonous hairs.

The earlier studies seemed to indicate that the irritation was
purely mechanical in origin, the result of the minute barbed hairs

36. Browntail moths. One male and two females. Photograph by
M.V. S.

working into the skin in large numbers. Subsequently, however,
Dr. Tyzzer (1907) demonstrated beyond question that the trouble
was due to a poison contained in the hairs. In the first place, it is
only the peculiar short barbed hairs which will produce the dermatitis
when rubbed on the skin, although most of the other hairs are sharply
barbed. Moreover, it was found that in various ways the nettling
properties could be destroyed without modifying the structure of the
hairs. This was accomplished by baking for one hour at no° C, by
warming to 6o° C in distilled water, or by soaking in one per cent, or in
one-tenth per cent, of potassium hydrate or sodium hydrate. The
most significant part of his work was the demonstration of the fact

Poisonous Arthropods

that if the nettling hairs are mingled with blood, they immediately
produce a change in the red corpuscles. These at once become

coarsely crenated, and the
roleaux are broken up in the
vicinity of the hair (fig. 37 b).
The corpuscles decrease in
size, the coarse crenations
are transformed into slender
spines which rapidly disap¬
pear, leaving the corpuscles
in the form of spheres, the
light refraction of which con¬
trasts them sharply with the
normal corpuscles. The
reaction always begins at the

(a) Ordinary hairs and three poison hairs of sub- . . , . , r ., , •

dorsal and lateral tubercles of the larva of the basal Sharp pOUlt OI the hair.
browntail moth. Drawing by Miss Kephart. R ^ ^ produced by

purely mechanical means, such as the mingling of minute par¬
ticles of glass wool, the barbed hairs of a tussock moth, or the other
coarser hairs of the brown-tail, with the blood.

The question of the source of the poison has been studied in our
laboratory by Miss Cornelia

37.

Kephart. She first confirmed
Dr. Tyzzer’s general results
and then studied carefully fixed
specimens of the larvae to
determine the distribution of
the hairs and their relation to
the underlying tissues.

The poison hairs (fig. 37),
are found on the subdorsal
and lateral tubercles (fig. 38),
in bunches of from three to
twelve on the minute papillae
with which the tubercles are
thickly covered. The under¬
lying hypodermis is very
greatly thickened, the cells
being three or four times the length of the ordinary hypodcrmal
cells and being closely crowded together. Instead of a pore canal

37.

(6) Effect of the poison on the blood cor¬
puscles of man. After Tyzzer.

Nettling Insects

through the cuticula for each individual hair, there is a single pore
for each papillae on a tubercle, all the hairs of the papilla being

connected with the
underlying cells
through the same
pore canal, (figs.
39 and 40).

The hypodermis
of this region is of
two distinct types
of cells. First,
there is a group of
slender fusiform
cells, one for each
poison hair on the
papilla, which are
the trichogen, or
hair-formative cells. They are crowded to one side and towards
the basement membrane by a series of much larger, and more promi¬
nent cells (fig. 40), of which there is a single one for each papilla.
These larger cells have a granular protoplasm with large nuclei and
are obviously actively secreting. They are so characteristic in
appearance as to leave no question but that they are the true
poison glands.

Poisonous larvae of many other species have been reported from
Europe and especially from the tropics but the above-mentioned
species are the more important of those occurring in the United States
and will serve as types. It should be noted in this connection that

38. Cross section of the larva of the browntail moth showing the
tubercles bearing the poison hairs. Drawing by Miss
Kephart.

39. Epithelium underlying poison hairs of the larva of the
browntail moth. Drawing by Miss Kephart.

5 2

Poisonous Arthropods

40. Same as figure 39, on larger scale.

through some curious mis¬
understanding Goeldi (1913)
has featured the larva of
Orgyia leucostigma , the white-
marked tussock moth, as the
most important of the poi¬
sonous caterpillars of this
country. Though there are
occasional reports of irritation
from its hairs such cases are
rare and there is no evidence
that there is any poison pres¬
ent. Indeed, subcutaneous
implantation of the hairs
leads to no poisoning, but merely to temporary irritation.

Occasionally, the hairs of certain species of caterpillars find lodge¬
ment in the conjunctiva, cornea, or iris of the eye of man and give
rise to the condition known as opthalmia nodosa. The essential
feature of this trouble is a nodular conjunctivitis which simulates
tuberculosis of the conjunctiva and hence has been called pseudo-
tubercular. It may be distinguished microscopically by the presence
of the hairs.

Numerous cases of opthalmia nodosa are on record. Of those
from this country, one of the most interesting is reported by de
Schweinit z and
Shumway (1904). It
is that of a child of
fifteen years whose
eye had become in¬
flamed owing to the
presence of some for¬
eign body. Down¬
ward and inward on
the bulbar conjunc¬
tiva were a number
of flattened, grayish-
yellow nodules, be¬
tween which was a
marked congestion of

+ mn iiinr'-ti-u-ol 41 - Nodular conjunctivitis in the eye of a child.

tne conjunctival and DeSchwcinitz and Shumway.

Nettling Insects

episcleral vessels (fig. 41a). Twenty-seven nodules could be differ¬
entiated, those directly in the center of the collection being some¬
what confluent and
assuming a crescen¬
tic and circular ap¬
pearance. The nod¬
ules were excised
and, on sectioning,
were found to be
composed of a layer
of spindle cells and
round cells, outside
of which the tissue
was condensed into
a capsule. The
interior consisted of
epithelioid cells, be¬
tween which was a
considerable inter¬
cellular substance. Directly in the center of a certain number of
nodules was found the section of a hair (fig. 416). The evidence
indicated that the injury had resulted from playing with caterpillars
of one of the Arctiid moths, Spilosoma virginica. Other reported
cases have been caused by the hairs of larvae of Lasiocampa rubi,
L. pini, Porthetria dispar, Psilura monacha and Cnethocampa
processionea.

Relief from Poisoning by Nettling Larvae—The irritation from
nettling larvae is often severe and, especially in regions where the
brown-tail abounds, inquiries as to treatment arise. In general, it
may be said that cooling lotions afford relief, and that scratching,
with the possibilities of secondary infection, should be avoided, in
so far as possible.

Among the remedies usually at hand, weak solutions of ammonia,
or a paste of ordinary baking soda are helpful. Castellani and Chalm¬
ers recommend cleaning away the hairs by bathing the region with
an alkaline lotion, such as two per cent solution of bicarbonate of
soda, and then applying an ointment of ichthyol (10%).

Poisonous Arthropods

In the brown-tail district, there are many proprietary remedies of
which the best ones are essentially the following, as recommended
by Kirkland (1907):

Carbolic acid. drachm.

Zinc oxide. }4 oz.

Lime water. 8 oz.

Shake thoroughly and nib well into the affected parts.

In some cases, and especially where there is danger of secondary
infection, the use of a weak solution of creoline (one teaspoonful to a
quart of water), is to be advised.

Vescicating Insects and those Possessing Other Poisons in
their Blood Plasma

We have seen that certain forms, for example, the
poisonous spiders, not only secrete a toxine in their
poison glands, but that such a substance may be ex¬
tracted from other parts of their body, or even their
eggs. There are many insects which likewise possess a
42a. Blister bee- poisonous blood plasma. Such forms have been well

tie.

designated by Taschenberg as cryptotoxic (xpuxTO<; =
hidden). We shall consider a few representative forms.

The Blister Beetles —Fore¬
most among the cryptotoxic
insects are the Meloidce or
“blister beetles,” to which the
well-known “Spanish fly” (fig.
42a), formerly very generally
used in medical practice, be¬
longs. The vescicating property
is due to the presence in the
blood plasma of a peculiar,
volatile, crystalline substance
known as cantharidin, which is
especially abundant in the repro¬
ductive organs of the beetle. Ac¬
cording to Robert, the amount
of this varies in different species
from .4 or .5% to 2.57% of the
dry weight of the beetle.

426. An American blister beetle. Meloe an-
gusticollis. Photograph by M. V. S.

Vescicating Insects

While blister beetles have been especially used for external applica¬
tion, they are also at times used internally as a stimulant and a
diuretic. The powder or extract was formerly much in vogue as an
aphrodisiac, and formed the essential constituent of various philters,
or “love powders”. It is now known that its effects on the reproduc¬
tive organs appear primarily after the kidneys have been affected to
such an extent as to endanger life, and that many cases of fatal poison
have been due to its ignorant use.

There are many cases on record of poisoning and death due to
internal use, and in some instances from merely external application.
There are not rarely cases of poisoning of cattle from feeding on
herbage bearing a large number of the beetles and authentic cases are
known of human beings who have been poisoned by eating the flesh
of such cattle. Robert states that the beetles are not poisonous to
birds but that the flesh of birds which have fed on them is poisonous
to man, and that if the flesh of chickens or frogs which have fed on
the cantharidin be fed to cats it causes in them the same symptoms
as does the cantharidin.

Treatment of cases of cantharidin poison is a matter for a skilled
physician. Until he can be obtained, emetics should be administered
and these should be followed by white of egg in water. Oils should
be avoided, as they hasten the absorption of the poison.

Other Cryptotoxic Insects —Though the blister beetles are the
best known of the insects with poisonous blood plasma, various
others have been reported and we shall refer to a few of the best
authenticated.

One of the most famous is the Chrysomelid beetle, Diamphidia
simplex , the bod) 7 fluids of whose larvae are used by certain South
African bushmen as an arrow poison. Its action is due to the presence
of a toxalbumin which exerts a haemolytic action on the blood, and
produces inflammation of the subcutaneous connective tissue and
mucous membranes. Death results from general paralysis. Krause
(1907) has surmised that the active principle may be a bacterial toxine
arising from decomposition of the tissues of the larva, but he presents
no support of this view and it is opposed by all the available evidence.

In China, a bug, Heuchis sanguined, belonging to the family
Cicadidfe, is used like the Meloidas, to produce blistering, and often
causes poisoning. It has been assumed that its vescicating properties
are due to cantharidin, but the presence of this substance has not
been demonstrated.

Poisonous Arthropods

Certain Aphididae contain a strongly irritating substance which
produces, not merely on mucous membranes but on outer skin, a
characteristic inflammation.

It has been frequently reported that the larvae of the Eurpoean
cabbage butterfly, Pieris brassiere, accidentally eaten by cows, horses,
ducks, and other domestic animals, cause severe colic, attempts to
vomit, paralysis of the hind legs, salivation, and stomatitis. On
postmortem there are to be found haemorrhagic gastro-enteritis,
splenitis, and nephritis. Kobert has recently investigated the subject
and has found a poisonous substance in the blood of not only the
larvae but also the pupae.

CHAPTER III

PARASITIC ARTHROPODA AFFECTING MAN

The relation of insects to man as simple parasites has long been
-studied, and until very recent years the bulk of the literature of medi¬
cal entomology referred to this phase of the subject. This is now
completely overshadowed by the fact that so many of these parasitic
forms are more than simple parasites, they are transmitters of other
microscopic parasites which are pathogenic to man. Yet the impor¬
tance of insects as parasites still remains and must be considered in a
discussion of the relation of insects to the health of man. In taking
up the subject we shall first consider some general features of the
phenomenon of animal parasitism.

Parasitism is an adaptation which has originated very often among
living organisms and in widely separated groups. It would seem
simple to define what is meant by a “parasite” but, in reality, the
term is not easily limited. It is often stated that a parasite is “An
organism which lives at the expense of another,” but this definition
is applicable to a predatory species or, in its broadest sense, to all
organisms. For our purpose we may say with Braun: “A parasite
is an organism which, for the purpose of obtaining food, takes up its
abode, temporarily or permanently, on or within another living
organism”.

Thus, parasitism is a phase of the broad biological phenomenon of
symbiosis , or living together of organisms. It is distinguished from
mutualism, or symbiosis in the narrow sense, by the fact that only one
party to the arrangement obtains any advantage, while the other is
to a greater or less extent injured.

Of parasites we may distinguish on the basis of their location on or
in the host, ecto-parasites, which live outside of the body; and endo-
parasites, which live within the body. On account of their method
of breathing the parasitic arthropods belong almost exclusively to the
first of these groups.

On the basis of relation to their host, we find temporary parasites,
those which seek the host only occasionally, to obtain food; and the
stationary or permanent parasites which, at least during certain stages,
do not leave their host.

Facultative parasites are forms which are not normally parasitic,
but which, when accidentally ingested, or otherwise brought into the

Parasitic Arthropods

body, are able to exist for a greater or less period of time in their
unusual environment. These are generally called in the medical
literature “pseudoparasites” but the term is an unfortunate one.

We shall now take up the different groups of arthropods, discussing
the more important of the parasitic forms attacking man. The
systematic relationship of these forms, and key for determining
important species will be found in Chapter XII.

Acarina or Mites

The Acarina, or mites , form a fairly natural group of arachnids,
characterized, in general, by a sac-like, unsegmented body which is
generally fused with the cephalothorax. The mouth-parts have been
united to from a beak or rostrum.

The representatives of this group undergo a marked metamor¬
phosis. Commonly, the larvae on hatching from the egg, possess but
three pairs of legs, and hence are called hexapod larvae. After a molt,
they transform into nymphs which, like the adult, have four pairs of
legs and are called octopod nymphs. These after a period of growth,
molt one or more times and, acquiring external sexual organs, become
adult.

Most of the mites are free-living, but there are many parasitic
species and as these have originated in widely separated families, the
Acarina form an especially favorable group for study of the origin of
parasitism. Such a study has been made by Ewing (1911), who has
reached the following conclusions:

“We have strong evidence indicating that the parasitic habit has
originated independently at least eleven times in the phvlogeny of the
Ararina. Among the zoophagous parasites, the parasitic habit has
been developed from three different types of free-living Acarina:
(a) predaceous forms, (b) scavengers, (c) forms living upon the juices
of plants.”

Ewing also showed that among the living forms of Acarina we can
trace out ah the stages of advancing parasitism, semiparasitism,
facultative parasitism, even to the fixed and permanent type, and
finally to cndoparasitism.

Of the many parasitic forms, there are several species which are
serious parasites of man and we shall consider the more important of
these. Infestation by mites is technically known as acariasis.

A carina, or Mites

43. Effect of the harvest mites on the skin of man. Photograph by
J. C. Bradley.

■6o

Parasitic Arthropods

The Trombidiidae, or Harvest Mites

In many parts of this country it is impossible for a visitor to go
into the fields and, particularly, into berry patches and among tall
weeds and grass in the summer or early fall without being affected by
an intolerable itching, which is followed, later, by a breaking out of
wheals, or papules, surrounded by a bright red or violaceous aureola,
(fig. 43). It is often regarded as a urticaria or eczema, produced by
change of climate, an error in diet, or some condition of general health.

Sooner or later, the victim finds that it is due to none of these, but
to the attacks of an almost microscopic red mite, usually called
"“jigger” or “chigger” in this country. As the term “chigger” is
applied to one of the true fleas, Dermatophilus penetrans, of the tropics,

these forms are more
correctly known as
“harvest mites.”
N atives of an infested
region may be so

immune or accus¬

tomed to its attacks
as to be unaware of
its presence, though
such immunity is by
no means possessed
by all who have been

44. Harvest mites. (Larvae of Trombidium). After C. V. , " , . ..

Riley. long exposed to the

annoyance.

The harvest mites, or chiggers, attacking man are larval forms,
possessing three pairs of legs (fig. 44). Their systematic position was
at first unknown and they were classed under a special genus Leptus,
a name which is very commonly still retained in the medical literature.
It is now known that they are the larval forms of various species of
the genus Trombidium, a group of predaceous forms, the adults of
which feed primarily on insects and their eggs. In this country the
species best known are those to be found late in summer, as larvae
at the base of the wings of houseflies or grasshoppers.

There is much uncertainty as to the species of the larvae attacking
man but it is clear that several are implicated. Bruvant has shown
that in France the larvae Trombidium inapinatum and Trombidium
holosericeum are those most frequently found. The habit of attacking
man is abnormal and the larvae die after entering the skin. Normally
they are parasitic on various insects.

The Harvest Mites

Most recent writers agree that, on man, they do not bore into the
skin, as is generally supposed, but enter a hair follicle or sebaceous
gland and from the bottom of this, pierce the cutis with their elongate
hypopharynx. According to Braun, there arises about the inserted
hypopharynx a fibrous secretion — the so-called “beak” which is, in
reality, a product of the host. Dr. J. C. Bradley, however, has made
careful observations on their method of attack, and he assures us that
the mite ordinarily remains for a long time feeding on the surface of
the skin, where it produces the erythema above described. During
this time it is not buried in the skin but is able to retreat rapidly into
it through a hair follicle or sweat gland. The irritation from the
mites ceases after a few days, but not infrequently the intolerable
itching leads to so much scratching that secondary infection follows.

Relief from the irritation may be afforded by taking a warm salt
bath as soon as possible after exposure or by killing the mites by
application of benzine, sulphur ointment or carbolized vaseline.
When they are few in number, they can be picked out with a sterile
needle.

Much may be done in the way of warding off their attacks by
wearing gaiters or close-woven stockings extending from ankle to the
knee. Still more efficacious is the sprinkling of flowers of sulphur in
the stockings and the underclothes from a little above the knee, down.
The writers have known this to make it possible for persons who were
especially susceptible to work with perfect comfort in badly infested
regions. Powdered naphthalene is successfully used in the same way
and as Chittenden (1906) points out, is a safeguard against various
forms of man-infesting tropical insect pests.

The question of the destruction of the mites in the field is some¬
times an important one, and under some conditions, is feasible.
Chittenden states that much can be accomplished by keeping the
grass, weeds, and useless herbage mowed closely, so as to expose the
mites to the sun. He believes that in some cases good may be done
by dusting the grass and other plants, after cutting, with flowers of
sulphur or by spraying with dilute kerosene emulsion in which
sulphur has been mixed. More recently (1914) he calls attention to
the value of cattle, and more especially sheep, in destroying the pests
by tramping on them and by keeping the grass and herbage closely
cropped.

Parasitic Arthropods
IxODOIDEA OR TlCKS

Until recently, the ticks attracted comparatively little attention
from entomologists. Since their importance as carriers of disease

has been established, interest in
the group has been enormously
stimulated and now they rank
second only to the mosquitoes
in the amount of detailed study
that has been devoted to them.

The ticks are the largest of
the Acarina. They are char¬
acterized by the fact that the
hypostome, or “tongue” (fig. 45)
is large and file-like, roughened
by sharp teeth. They possess
a breathing pore on each side
of the body, above the third
or fourth coxae (fig. 45 b).

There are two distinct fami¬
lies of the Ixodoidea, differing
greatly m structure, lite-history and habits. These are the Argasidae
and the Ixodidae. We shall follow Nuttall (1908) in characterizing
these two families and in pointing out their biological differences, and
shall discuss briefly the more important species which attack man.
The consideration of the
ticks as carriers of disease
will be reserved for a later
chapter.

Argasidae

In the ticks belonging to
the family Argasidae, there
is comparatively little sexual
dimorphism, while this is
very marked in the Ixodidae.

The capitulum, or so-called
“head” is ventral, instead of
terminal; the palpi are leg¬
like, with the segments subequal; the scutum, or dorsal shield, is
absent; eyes, when present, are lateral, on supracoxal folds. The

45 a. Argus persicus. Capitulum of male
After Nuttall and Warburton.

Ixodoidea, or Ticks 63

spiracles are very small; coxae unarmed; tarsi without ventral spurs,
and the pul villi are absent or rudimentary.

In habits and life history' the Argasidae present striking characteris¬
tics. In the first place, they are long-lived, a factor which counts for
much in the maintenance of the species. They are intermittent
feeders, being comparable with the bed-bug in this respect. There are
two or more nymphal stages, and they may* molt after attaining matu¬
rity. The female lays comparatively' few eggs in several small batches.

Nuttall (1911) concludes that “The Argasidae represent the rela¬
tively^ primitive type of ticks because they' are less constantly para-

46. Argus persicus. Dorsal and ventral aspects. (X 4). After Hassell.

sitic than are the Ixodidae. Their ny'mphs and adults are rapid
feeders and chiefly' infest the habitat of their hosts. * * * Owing

to the Argasidas infesting the habitats of their hosts, their resistance
to prolonged starvation and their rapid feeding habits, they do not
need to bring forth a large progeny', because there is less loss of life
in the various stages, as compared with the Ixodidae, prior to their
attaining maturity.’’

Of the Argasidae, we have in the United States, several species
which have been reported as attacking man.

Argas persicus, the famous “Miana bug’’ (fig. 46), is a very widely
distributed species, being reported from Europe, Asia, Africa, and
Australia. It is every "where preeminently a parasite of fowls.

Parasitic Arthropods

According to Nuttall it is specifically identical with Argas americanus
Packard or Argas miniatus Koch, which is commonly found on fowls-

in the United States, in the South
and Southwest. Its habits are com¬
parable to those of the bed-bug. It
feeds intermittently, primarily at
night, and instead of remaining on its
host, it then retreats to cracks and
crevices. Hunter and Hooker (1908)
record that they have found the larva
to remain attached for five or eight
days before dropping. Unlike the
Ixodidae, the adults oviposit fre¬
quently.

The most remarkable feature of

the biology of this species is the great

47 . Otiobius (Ornithodoros) megnini, head longevity, especially of the adult,
of nymph. After Stiles. & J ^ J

Hunter and Hooker report keeping
larvae confined in summer in pill boxes immediately after hatch¬
ing for about two months while under similar conditions those
of the Ixodid, Boophilus annulatus lived for but two or three days.

48. Otiobius (Ornithodoros) megnini, male, (a) dorsal, (6) ventral
aspect. After Nuttall and Warburton.

Many writers have recorded keeping adults for long periods without
food. We have kept specimens in a tin box for over a year and a half
and at the end of that time a number were still alive. Laboullicne
kept unfed adults for over three years. In view of the effectiveness of

Ixodoidea , or Ticks

sulphur in warding off the attacks of Trombidiidae, it is astonishing
to find that Lounsbury has kept adults of Argas persicus for three
months in a box nearly filled with flowers of sulphur, with no apparent
effect on them.

We have already called attention to the occasional serious effects
of the bites of this species. While such reports have been frequently
discredited there can be no doubt that they have foundation in fact.
The readiness with which this tick attacks man, and the extent to
which old huts may be infested makes it especially troublesome.

Otiobius ( Ornithodoros) megnini, the “spinose ear-tick ’’(figs. 47,48),
first described from Mexico, as occurring in the ears of horses, is a
common species in our Southwestern States and is recorded by Banks
as occurring as far north as Iowa.

The species is remarkable for the great difference between the
spiny nymph stage and the adult. The life history has been worked
out by Hooker (1908). Seed ticks, having gained entrance to the
ear, attach deeply down in the folds, engorge, and in about five days,
molt; as nymphs with their spinose body they appear entirely unlike
the larvae. As nymphs they continue feeding sometimes for months.
Finally the nymph leaves the host, molts to form the unspined adult,
and without further feeding is fertilized and commences oviposition.

The common name is due to the fact that in the young stage the
ticks occur in the ear of their hosts, usually horses or cattle. Not
uncommonly it has been reported as occurring in the ear of man and
causing very severe pain. Stiles recommends that it be removed by
pouring some bland oil into the ear.

Banks (1908) reports three species of Ornithodoros — O. turicata,
coriaceus and talaje —as occurring in the United States. All of these
attack man and are capable of inflicting very painful bites.

Ixodidae

The ticks belonging to the family Ixodidae (figs. 49 and 50) exhibit
a marked sexual dimorphism. The capitulum is anterior, terminal,
instead of ventral as in the Argasidae; the palpi are relatively rigid
(except in the subfamily Ixodinae), with rudimentary fourth segment;
scutum present; eyes, when present, dorsal, on side of scutum. The
spiracles are generally large, situated well behind the fourth coxae;
coxae generally with spurs; pulvilli always present.

In habits and life history the typical Ixodidae differ greatly from
the Argasidae. They are relatively short-lived, though some recent

Parasitic Arthropods

work indicates that their long¬
evity has been considerably
under-estimated. Typically,
they are permanent feeders,
remaining on the host, or hosts,
during the greater part of their
life. They molt twice only,
on leaving the larval and the
nymphal stages. The adult
female deposits a single, large
batch of eggs. Contrasting
the habits of the Ixodidae to
those of the Argasidae, Nuttall
(1911) emphasizes that the
Ixodidae are more highly
specialized parasites. “The
majority are parasitic on hosts
having no fixed habitat and
consequently all stages, as a
rule, occur upon the host.”

As mere parasites of man, apart from their power to transmit
disease, the Ixodidae are much less important than the Argasidae.
Many are reported as occasionally attacking man and of these the
following native spe¬
cies may be mentioned.

Ixodes ricinus, the
European castor bean
tick (figs. 49, 50), is a
species which has been
often reported from
this country but Banks
(1908) lias shown that,
though it does occur,
practically all of the
records apply to Ixodes
scapularis or Ixodes
cookei. In Europe,

Ixodes ricinus is very
abundant and very
commonly attacks

50. Ixodes ricinus, var. scapularis, female. Capitulum and
scutum; ventral aspect of capitulum- coxse; tarsus 4;
spiracle; genital and anal grooves. After Nuttall and
Warburton.

Ixodoidea, or Ticks

man. At the point of penetration of the hypostome there is more or
less inflammation but serious injury does not occur unless there have
been introduced pathogenic bacteria or, unless the tick has been
abruptly removed, leaving the capitulum in the wound. Under the
latter circumstances, there maybe an abscess formed about the foreign
body and occasionally, serious results have followed. Under certain
conditions the tick, in various stages, may penetrate under the skin
and produce a tumor, within which it may survive for a considerable
period of time.

Ixodes cookei is given by Banks as “common on mammals in the
Eastern States as far west as the Rockies.” It is said to affect man
severely.

Amblyomma americanwn, (fig. 158c), the “lone star tick,” is
widely distributed in the United States. Its common name is derived
from the single silvery spot on the scutum of the female. Hunter
and Hooker regard this species as, next to Boophilus annulatus, the
most important tick in the United States. Though more common on
cattle, it appears to attack mammals generally, and “in portions of
Louisiana and Texas it becomes a pest of considerable importance to
moss gatherers and other persons who spend much time in the forests.”

Amblyomma cajennense, noted as a pest of man in central and
tropical America, is reported from various places in the south and
southwestern United States.

Dermacentor variabilis is a common dog tick of the eastern United
States. It frequently attacks man, but the direct effects of its bite
are negligible.

The “ Rocky Mountian spotted fever tick” ( Dermacentor andersoni
according to Stiles, D. venustus according to Banks) is, from the view¬
point of its effects on man, the most important of the ticks of the
United States. This is because, as has been clearly established, it
transmits the so-called “spotted fever” of man in our northwestern
states. This phase of the subject will be discussed later and it need
merely be mentioned here, that this species has been reported as
causing painful injuries by its bites. Dr. Stiles states that he has
seen cases of rather severe lymphangitis and various sores and swell¬
ings developing from this cause. In one case, of an individual bitten
near the elbow, the arm became very much swollen and the patient
was confined in bed for several days. The so-called tick paralysis
produced by this species is discussed in a preceding chapter.

Parasitic Arthropods

There are many other records of various species of ticks attacking
man, but the above-mentioned will serve as typical and it is not neces¬
sary to enter into greater detail.

Treatment of Tick Bites —When a tick attaches to man the first
thing to be done is to remove it without leaving the hypostome in the
wound to fester and bring about secondary effects. This is best
accomplished by applying to the tick’s body some substance which
will cause it to more readily loosen its hold. Gasoline or petroleum,

oil or vaseline will serve.
For removing the
spinose ear-tick, Stiles
recommends pouring
some bland oil into the
ear. Others have used
effectively a pledget of
cotton soaked in chloro¬
form.

In general, the treat¬
ment recommended by
Wellman for the bites
of Ornithodoros moubata
vail prove helpful. It
consists of prolonged
bathing in very hot
water, followed by the

51 . Dermanyssus gallinae. female. After Delafond. application of a Strong

solution of bicarbonate

of soda, which is allowed to dry upon the skin. He states that this
treatment is comforting. For severe itching he advises smearing
the bites with vaseline, which is slightly impregnated with camphor
or menthol. Medical aid should be sought when complications arise.

The Dermanyssidae are Gamasid mites which differ from others of
the group in that they are parasitic on vertebrates. None of the
species normally attack man, but certain of them, especially the
poultry mite, may be accidental annoyances.

Dermanyssus gallince (fig. 51), the red mite of poultry, is an exceed¬
ingly common and widespread parasite of fowls. During the day
it lives in cracks and crevices of poultry houses, under supports of
roosts, and in litter of the food and nests, coming out at night to feed.

Tarsonemidce

They often attack people working in poultry houses or handling and
plucking infested fowls. They may cause an intense praritis, but they

do not produce a true dermatosis, for
they do not find conditions favorable for
multiplication on the skin of man.

Tarsonemidae

The representatives of the family Tar¬
sonemidae are minute mites, with the body
divided into cephalothorax and abdomen.
There is marked sexual dimorphism.
The females possess stigmata at the
anterior part of the body, at the base of
the rostrum, and differ from all other mites
in having on each side, a prominent clavate
organ between the first and second legs.
52 ' P ma^ loi AfLr V Webs C t°er US ’ fe " The l arva > when it exists, is hexapodous

and resembles the adult. A number of the
species are true parasites on insects, while others attack plants.
Several of them may be accidental parasites of man.

Pediculoides ventricosus
(fig. 52 and 53) is, of all the
Tarsonemidae reported, the
one which has proved most
troublesome to man. It is a
predaceous species which
attacks a large number of
insects but which has most
commonly been met with by
man through its fondness for
certain grain-infesting insects,
notably the Angoumois grain
moth, Sitotroga cerealella, and
the wheat straw-worm, Iso¬
soma grande. In recent years
it has attracted much atten¬
tion in the United States and
its distribution and habits
have been the object of detail-

W,, T_/ _ \ 53. Pediculoides ventricosus, gravid female. (X SO)

Study by Webster (1901). After Webster.

Parasitic Arthropods

There is a very striking sexual dimorphism in this species. The
non-gravid female is elongate, about 2009, by yojx (fig. 52), with the
abdomen slightly striated longitudinally. The gravid female (fig. 53)
has the abdomen enormously swollen, so that it is from twenty to a
hundred times greater than the rest of the body. The species is-
viviparous and the larva' undergo their entire growth in the body of
the mother. They emerge as sexually mature males and females
which soon pair. The male (fig. 54) is much smaller, reaching a

length of only 3 20^ but
is relatively broad,
8c| jl, and angular. Its
abdomen is very great¬
ly reduced.

As far back as 1850
it was noted as caus¬
ing serious outbreaks
of peculiar dermatitis
among men handling
infested grain. For
some time the true
source of the difficulty
was unknown and it
was even believed that
the grain had been
poisoned. Webster
has shown that in this
country (and probably
in Europe as well) its
attacks have been mistaken for those of the red bugs or “chiggers”
(larval Trombiidse). More recently a number of outbreaks of a
mysterious “skin disease” were traced to the use of straw mattresses,
which were found to be swarming with these almost microscopic
forms which had turned their attentions to the occupants of the beds.
Other cases cited were those of farmers running wheat through a
fanning mill, and of thrashers engaged in feeding unthrashed grain
into the cylinder of the machine.

The medical aspects of the question have been studied especially
by Schamberg and Goldbergcr and from the latter’s summary (1910)
we derive the following data. Within twe ve to sixteen hours after
exposure, itching appears and in severe cases, especially where expo-

Pediculoides Ventricosus

7 i

sure is continued night after night by sleeping on an infested bed, the
itching may become almost intolerable. Simultaneously, there
appears an eruption which characteristically consists of wheals
surrounded by a vesicle (fig. 55). The vesicle as a rule does not exceed
a pin head in size but may become as large as a pea. Its contents

55. Lesions produced by the attacks of Pediculoides ventri-
cosus. After Webster.

rapidly become turbid and in a few hours it is converted into a pustule.
The eruption is most abundant on the trunk, slight on the face and
extremities and almost absent on the feet and hands. In severe cases
there may be constitutional disturbances marked, at the outset, by
chilliness, nausea, ajid vomiting, followed for a few days by a slight
elevation of temperature, with the appearance of albumin in the
urine. In some cases the eruption may simulate that of chicken-pox
or small-pox.

Parasitic Arthropods

Treatment for the purpose of killing the mites is hardly necessary
as they attach feebly to the surface and are readily brushed off by
friction of the clothes. “Antipruritic treatment is always called for;
warm, mildly alkaline baths or some soothing ointment, such as zinc
oxide will be found to fulfil this indication.’’ Of course, reinfestation
must be guarded against, by discarding, or thoroughly fumigating
infested mattresses, or by avoiding other sources. Goldberger sug¬
gests that farm laborers who must work with infested wheat or straw
might protect themselves by anointing the body freely with some
bland oil or grease, followed by a change of clothes and bath as soon
as their work is done. We are not aware of any experiments to
determine the effect of flowers of sulphur, but their efficiency in the
case of “red bugs” suggests that they are worth a trial against
Pediculoides.

Various species of Tyroglyphidae (fig. 150/) may abound on dried
fruits and other products and attacking persons handling them, may
cause a severe dermatitis, comparable to that described above for
Pediculoides ventricosus. Many instances of their occurrence as such
temporary ectoparasites are on record. Thus, workers who handle
vanilla pods are subject to a severe dermatitis, known as vanillism,
which is due to the attacks of Tyroglyphus siro, or a closely related
species. The so-called “grocer’s itch” is similarly caused by mites
infesting various products. Castellani has shown that in Ceylon,
workers employed in the copra mills, where dried cocoanut is ground
up for export, are much annoyed by mites, which produce the so-called
“copra itch.” The skin of the hands, arms and legs, and sometimes
of the whole body, except the face,is covered by fairly numerous, very
pruriginous papules, often covered by small, bloody crusts due to
scratching. The condition is readily mistaken for scabies. It is
due to the attacks of Tyroglyphus longior castellanii which occur in
enormous numbers in some samples of the copra.

Sarcoptidae

The Sarcoptidae are minute whitish mites, semi-globular in shape,
with a delicate transversely striated cuticula. They lack eyes and
tracheae. The mouth-parts are fused at the base to form a cone
which is usually designated as the head. The legs are short and
stout, and composed of five segments. The tarsi may or may not
possess a claw and may terminate in a pedunculated sucker, or simple
long bristle, or both. The presence or absence of these structures

Sarcoptidce, or Itch Mites

and their distribution are much used in classification. The mites
live on or under the skin of mammals and birds, where they produce

the disease known as scabies, mange, or
itch. Several species of the Sarcoptidae
attack man but the most important of
these, and the one pre-eminent as the
“itch mite” is Sarcoptes scabiei.

The female of Sarcoptes scabiei, of man,
is oval and yellowish white; the male
more rounded and of a somewhat reddish
tinge, and much smaller. The body is
marked by transverse stria? which are
partly interrupted on the back. There
are transverse rows of scales, or pointed
spines, and scattered bristles on the
dorsum.

The male (fig. 56) which is from 200-
240^ in length, and 150-200^ in breadth,
possesses pedunculated suckers on each
pair of legs except the third, which bears, instead, a long bristle.
The female (fig. 56) 300-450^ in length and 2 5 o-3SO[a in breadth, has
the pedunculated suckers on the first and second pairs of legs, only,
the third and fourth terminating in bristles.

The mite lives in irregular galleries from
a few millimeters to several centimeters in
length, which it excavates in the epidermis
(fig. 57). It works especially where the
skin is thin, such as between the fingers,
in the bend of the elbows and knees, and
in the groin, but it is by no means restricted
to these localities. The female, alone,
tunnels into the skin; the males remain
under the superficial epidermal scales, and
seldom are found, as they die soon after
mating.

As she burrows into the skin the female
deposits her eggs, which measure about
150 x 100^. Fiirstenberg says that each
deposits an average of twenty-two to twenty-four eggs, though
Guddcn reports a single burrow as containing fifty-one. From these

56a. Sarcoptes scabiei, male.

(X 100). After Fiirsten-
berg.

Parasitic Arthropods

there develop after about seven days, the hexapod larvas. These
molt on the sixteenth day to form an octopod nymph, which molts
again the twenty-first day. At the end of the fourth week the
nymphs molt to form the sexually mature males and the so-called
pubescent females. These pair, the males die, and the females again
cast their skin, and become the oviparous females. Thus the life¬
cycle is completed in about twenty-eight days.

The external temperature exercises a great influence on the develop¬
ment of the mites and thus, during the winter, the areas of infesta¬
tion not only do not spread, but they become restricted. As soon as
the temperature rises, the mites increase and the infestation becomes-
much more extensive.

57. Sarcoptes scabiei. Diagrammatic representation of the course in
the skin of man.

In considering the possible sources of infestation, and the chances-
of reinfestation after treatment, the question of the ability of the mite
to live apart from its host is a very important one. Unfortunately,,
there are few reliable data on this subject. Gerlach found that,
exposed in the dry, warm air of a room they became very inactive
within twenty-four hours, that after two days they showed only
slight movement, and that after three or four days they could not
be revived by moisture and warming. The important fact was
brought out that in moist air, in folded soiled underwear, they sur¬
vived as long as ten days. Bourguignon found that under the most
favorable conditions the mites of Sarcoptes scabiei equi would live for
sixteen days.

The disease designated the “itch” or “scabies,” in man has been
known from time immemorial, but until within less than a hundred
years it was almost universally attributed to malnutrition, errors of

Sarcoptidce , or Itch Mites

diet, or ‘‘bad blood.” This was in spite of the fact that the mite was
known to Mouffet and that Bonomo had figured both the adult and
the egg and had declared the mite the sole cause of the disease. In
1834 the Corsican medical student, Francis Renucci, demonstrated
the mite before a clinic in Saint Louis Hospital in Paris and soon
thereafter there followed detailed studies of the life history of the

various itch mites of
man and animals.

The disease is a cos¬
mopolitan one, being ex¬
ceedingly abundant in
some localities. Its
spread is much favored
where large numbers of
people are crowded to¬
gether under insanitary
conditions and hence it
increases greatly during
wars and is widely dis¬
seminated and abundant
immediately afterwards.
Though more commonly
to be met with among
the lower classes, it not
infrequently appears
among those of the most
cleanly, careful habits,
and it is such cases that
are most liable to wrong
diagnosis by the physi¬
cian.

Infection occurs solely through the passage, direct or indirect,
of the young fertilized females to the skin of a healthy individual.
The adult, oviparous females do not quit their galleries and hence
do rot serve to spread the disease. The young females move about
more or less at night and thus the principal source of infestation is
through sleeping in the same bed with an infested person, or indirectly
through bedclothes, or even towels or clothing. Diurnal infestation
through contact or clothing is exceptional. Many cases are known
of the disease being contracted from animals suffering from scabies,
or mange.

08 . Scabies on the hand. From portfolio of Dermo-
chromes by permission of Rebman & Co., of
New York. Publisheis.

7 6

Parasitic Arthropods

When a person is exposed to infestation, the trouble manifests
itself after eight or ten days, though there usually elapses a period of

twenty to thirty days be¬
fore there is a suspicion of
anything serious. The first
symptom is an intense
itching which increases
when the patient is in bed.
When the point of irrita¬
tion is examined the gal¬
leries may usually be seen
as characteristic sinuous
lines, at first whitish in
color but soon becoming
blackish because of the con¬
tained eggs and excrement.
The galleries, which may
not be very distinct in
some cases, may measure
as much as four centi¬
meters in length. Little
vesicles, of the size of a

59. Scabies on the hand. After Duhring. . , . . , .

pm head are produced by
the secretions of the feeding mite; they are firm, and projecting, and
contain a limpid fluid. Figures 58
and 59 show the typical appearance
of scabies on the hands, while figure
60 shows a severe general infesta¬
tion. The intolerable itching induces
scratching and through this various
complications may arise. The lesions
are not normally found on the face
and scalp, and are rare on the back.

Formerly, scabies was considered
a very serious disease, for its cause
and method of treatment were un¬
known, and potentially it may con¬
tinue indefinitely. Generation after
generation of the mites may develop

and finally their number become so After Morrow.

Sarcoptidce, or Itch Mites

great that the general health of the individual is seriously affected.
Now that the true cause of the disease is known, it is easily con¬
trolled.

Treatment usually consists in softening the skin by friction with
soap and warm water, followed by a warm bath, and then applying
some substance to kill the mites. Stiles gives the following direc¬
tions, modified from Bourguignon’s, as “a rather radical guide, to
be modified according to facilities and according to the delicacy of the
skin or condition of the patient”:

i. The patient, stripped naked, is energetically rubbed all over
(except the head) for twenty minutes, with green soap and warm
water. 2. He is then placed in a warm bath for thirty minutes,
during which time the rubbing is continued. 3. The parasiticide
is next nibbed in for twenty minutes and is allowed to remain on the
body for four or five hours; in the meantime the patient’s clothes are
sterilized, to kill the eggs or mites attached to them. 4. A final
bath is taken to remove the parasiticide.

The parasiticide usually relied on is the officinal sulphur ointment
of the United States pharmacopoeia. When infestation is severe it
is necessary to repeat treatment after three or four days in order
to kill mites which have hatched from the eggs.

The above treatment is too severe for some individuals and may,
of itself, produce a troublesome dermatitis. We have seen cases
where the treatment was persisted in and aggravated the condi¬
tion because it was supposed to be due to the parasite. For deli¬
cate-skinned patients the use of balsam of Peru is very satisfac¬
tory, and usually causes no irritation whatever. Of course, sources
of reinfection should be carefully guarded against.

Sarcoptes scabiei crustosce, which is a distinct variety, if not species,
of the human itch mite, is the cause of so-called Norwegian itch.
This disease is very contagious, and is much more resistant than the
ordinary scabies. Unlike the latter, it may occur on the face and
scalp.

Sarcoptes scabiei not only attacks man but also occurs on a large
number of mammals. Many species, based on choice of host, and
minute differences in size and secondary characters, have been
established, but most students of the subject relegate these to
varietal rank. Many of them readily attack man, but they have
become sufficiently adapted to their normal host so that they are
usually less persistent on man.

Parasitic Arthropods

Notoedres cati (usually known as Sarcoptes minor) is a species
of itch mites which produce an often fatal disease of cats. The body
is rounded and it is considerably smaller than Sarcoptes scabiei ,
the female (fig. 61) measuring 215-230^ long and 165- 175^ wide;
the males 145-150^ by 120-125^. The most important character

61. Notoedres cati, male and female. After Railliet.

separating Notoedres from Sarcoptes is the position of the anus,
which is dorsal instead of terminal. The mite readily transfers
to man but does not persist, the infestation usually disappearing

spontaneously in about two weeks. Infested cats are
very difficult to cure, unless treatment is begun at

the very inception of the outbreak, and under ordi¬

nary circumstances it is better to kill them promptly,
to avoid spread of the disease to children and others
who may be exposed.

Demodecidae

The Demodecidae are small, elongate, vermiform
mites which live in the hair follicles of mammals.
The family characteristics will be brought out in the
discussion of the species infesting man, Demodex
folliculorum.

Demodex folliculorum (fig. 62) is to be found very
commonly in the hair follicles and sebaceous glands
of man. It is vermiform in appearance, and with the
elongate abdomen transversely striated so as to give

62 . Demodex foiii- it the appearance of segmentation. The female is 380-
Af tef 11 bi ar! ch ard! 400[A long by 45 ^; the male 300^ by 40^. The three-

Demodecidce, or Hair-follicle Mites

jointed legs, eight in number, are reduced to mere stubs in the adult.
The larval form is hexopod. These mites thus show in their form a
striking adaptation to their environment. In the sebaceous glands

Mtyzva d*J hth Jap Ercfvtt .Arts

Demode* follieulorum ( Owen )

63. Demodex follieulorum. Section through skin showing the
mites in situ. Magnification of Nos. 1, 2, 6 and 7, X 150;

Nos. 3 4, 5, X 450. After Megnin.

and hair follicles they lie with their heads down (fig. 63). Usually
there are only a few in a gland, but Gruby has counted as many as
two hundred.

The frequency with which they occur in man is surprising. Ac¬
cording to European statistics they are found in 50 per cent to 60 per
cent or even more. Gruby found them in forty out of sixty persons

Pa rasitic A rth ropods

examined. These figures arc very commonly quoted, but reliable
data for the United States seem to be lacking. Our studies indicate
that it is very- much less common in this country than is generally
assumed.

The Demodex in man does not, as a rule, cause the slightest
inconvenience to its host. It is often stated that they give rise to
comedons or “black-heads” but there is no clear evidence that they
are ever implicated. Certain it is that they are not the usual cause.
A variety of the same, or a very closely related species of Demodex,
on the dog gives rise to the very resistant and often fatal follicular
mange.

Hexapoda or True Insects

The Hexapoda, or true insects, arc characterized by the fact that
the adidt possesses three pairs of legs. The body is distinctly
segmented and is divided into head, thorax, and abdomen.

The mouth-parts in a generalized form, consist of an upper lip,
or labrum, which is a part of the head capsule, and a central unpaired
hypopharynx, two mandibles, two maxillce and a lower lip, or labium,
made up of the fused pair of second maxilla;. These parts may be
greatly modified, dependent upon whether they are used for biting,
sucking, piercing and sucking, or a combination of biting and sucking.

Roughly speaking, insects may be grouped into those which
undergo complete metamorphosis and those which have incomplete
metamorphosis. They are said to undergo complete metamorphosis
when the young form, as it leaves the egg, bears no resemblance to
the adult. For example, the maggot changes to a quiescent pupa
and from this emerges the winged active fly. They undergo incom¬
plete metamorphosis, when the young insect, as it leaves the egg,
resembles the adult to a greater or less extent, and after under¬
going a certain number of molts becomes sexually mature.

Representatives of several orders have been reported as accidental
or faculative parasites of man, but the true parasites are restricted
to four orders. These are the Siphunculata; the Hemiptera, the
Diptcra and the Siphonaptera.

Siphunculata

The order Siphunculata was established by Mcinert to include the
true sucking lice. These arc small wingless insects, with reduced
mouth-parts, adapted for sucking; thorax apparently a single piece
due to indistinct separation of its three segments; the compound eyes

Siphunculata, or Lice

reduced to a single ommatidium on each side. The short, powerful
legs are terminated by a single long claw. Metamorphosis incom¬
plete.

There has been a great deal of discussion regarding the structure
of the mouth-parts, and the relationships of the sucking lice, and the

questions cannot yet be re¬
garded as settled. The con¬
flicting views are well repre¬
sented by Cholodkovsky
(1904 and 1905) and by
Enderlein (1904).

Following Graber, it is
generally stated that the
mouth-parts consist of a
short tube furnished with
hooks in front, which consti¬
tutes the lower lip, and that within this is a delicate sucking tube
derived from the fusion of the labrum and the mandibles. Opposed
to this, Cholodkvosky and, more recently, Pawlowsky, (1906), have
shown that the piercing apparatus lies in a blind sac under the
pharynx and opening into the mouth cavity (fig. 64). It does not
form a true tube but a furrow with its open surface uppermost.
Eysell has shown that, in addition, there is a pair of chitinous rods
which he regards as the homologues of the maxillae.

When the louse feeds, it everts the anterior part of the mouth
cavity, with its circle of hooks. The latter serve for anchoring
the bug, and the piercing apparatus is then pushed
out.

Most writers have classed the sucking lice as a
sub-order of the Hemiptera, but the more recent
anatomical and developmental studies render this
grouping untenable. An important fact, bearing on
the question, is that, as shown by Gross, (1905),
the structure of the ovaries is radically different
from that of the Hemiptera.

. . . 65. P e d 1 c u 1 u s hu-

Lice infestation and its effects are known medi- manus, ventral as-

... pectofmale. (X 10)

cally as pediculosis. Though their continued pres¬
ence is the result of the grossest neglect and filthiness, the original
infestation may be innocently obtained and by people of the most
careful habits.

64. Pediculus showing the blind sac (6) containing the
mouth parts (a) beneath the alimentary canal
( p ). After Pawlowsky.

Parasitic Arthropods

Three species commonly attack man. Strangely enough, there
are very few accurate data regarding their life history.

Pediculus humanus (fig. 65), the head louse, is the most widely
distributed. It is usually referred to in medical literature as Pedi¬
culus capitis, but the Linnean specific name has priority. In color
it is of a pale gray, blackish on the margins. It is claimed by some
authors that the color varies according to the color of the skin of the

host. The abdomen is

composed of seven dis¬
tinct segments, bearing
spiracles laterally.
There is considerable
variation in size. The
males average 1.8 mm.
and the females 2.7 mm.
in length.

The eggs, fifty to
sixty in number, stick
firmly to the hairs of
the host and are known
as nits. They are large
and conspicuous, especi¬
ally on dark hair and
are provided with an
operculum, or cap, at
the free end, where the
nymphs emerge. They
hatch in about six days
and about the eigh¬
teenth day the young
lice are sexually mature.

The head lice live by preference on the scalp of their host but
occasionally they are found on the eyelashes and beard, or in the
pubic region. They may also occur elsewhere on the body The
penetration of the rostrum into the skin and the discharge of an irritat¬
ing saliva produce a severe itching, accompanied by the formation
of an eczema-like eruption (fig. 66). When the infestation is severe,
the discharge from the pustules mats down the hair, and scabs are
formed, under which the insects swarm. “ If allowed to run, a regular
carapace may form, called trichoma, and the head exudes a foetid

66 .

Pediculosis of the head. The illustration shows the
characteristic indications of the presence of lice, viz:
the occipital eczema gluing the hairs together, the
swollen cervical glands, and the porrigo, or erup¬
tion of contagious pustules upon the neck. After
Fox.

Pediculus Humanus 83

odor. Various low plants may grow in the trichoma, the whole
being known as -plica palonica.’ ’ — Stiles.

Sources of infestation are various. School children may obtain
the lice from seatmates, by wearing the hats or caps of infested mates,
or by the use, in common, of brushes and combs. They may be
obtained from infested beds or sleeper berths. Stiles reports an in¬
stance in which a large number of girls in a fashionable boarding
school developed lousiness a short time after traveling in a sleeping
car.

Treatment is simple, for the parasites may readily be controlled
by cleanliness and washing the head with a two per cent solution of
carbolic acid or even kerosene. The latter is better used mixed with
equal parts of olive oil, to avoid irritation. The treatment should
be applied at night and followed the next morning by a shampoo with
soap and warm water. It is necessary to repeat the operation in a
few days. Xylol, used pure, or with the addition of five per cent
of vaseline, is also very efficacious. Of course, the patient must be
cautioned to stay away from a lighted lamp or fire while using either
the kerosene or xylol. While these treatments will kill the eggs or
nits, they will not remove them from the hairs. Pusey recommends
repeated washings with vinegar or 2 5 per cent of acetic acid in water,
for the purpose of loosening and removing the nits.

Treatment of severe infestations in females is often troublesome
on account of long hair. For such cases the following method recom¬
mended by Whitfield (1912) is especially applicable:

The patient is laid on her back on the bed with her head over the
edge, and beneath the head is placed a basin on a chair so that the
hair lies in the basin. A solution of 1 in 40 carbolic acid is then poured
over the hair into the basin and sluiced backwards and forwards
until the whole of the hair is thoroughly soaked with it. It is especi¬
ally necessary that care should be taken to secure thorough satura¬
tion of the hair over the ears and at the nape of the neck, since these
parts are not only the sites of predilection of the parasites but they
are apt to escape the solution. This sluicing is carried out for ten
minutes by the clock. At the end of ten minutes the hair is lifted
from the basin and allowed to drain, but is not dried or even tho¬
roughly wrung out. The whole head is then swathed with a thick
towel or better, a large piece of common house flannel, which is
fastened up to form a sort of turban, and is allowed to remain thus
for an hour. It can then be washed or simply allowed to dry, as the

Parasitic Arthropods

carbolic quickly disperses. At the end of this period every pedicu-
lus and what is better, every ovum is dead and no relapse wall occur
unless there is exposure to fresh contagion. Whitfield states that
there seem to be no disadvantages in this method, which he has used
for years. He has never seen carboluria result from it, but would
advise first cutting the hair of children under five years of age.

Pediculus corporis (= P. vestimenti ) the body louse, is larger than
the preceding species, the female measuring 3.3 mm., and the male
3 mm. in length. The color is a dirty white, or grayish. P. corporis
has been regarded by some authorities as merely a variety of P.
humanus but Piaget maintains there are good characters separating
the two species.

The body louse lives in the folds and seams of the clothing of its
host, passing to the skin only when it wishes to feed. Brumpt
states that he has found enormous numbers of them in the collars
of glass-ware or grains worn by certain naked tribes in Africa.

Exact data regarding the life-history of this species have been
supplied, in part, by the work of Warburton (1910), cited by Nuttall.
He found that Pediculus corporis lives longer than P. humanus under
adverse conditions. This is doubtless due to its living habitually
on the clothing, whereas humanus lives upon the head, where it has
more frequent opportunities of feeding. He reared a single female
upon his own person, keeping the louse enclosed in a cotton-plugged
tube with a particle of cloth to which it could cling. The tube was
kept next to his body, thus simulating the natural conditions of
warmth and moisture under which the lice thrive. The specimen
was fed twice daily, while it clung to the cloth upon which it rested.
Under these conditions she lived for one month. Copulation com¬
menced five days after the female had hatched and was repeated a
number of times, sexual union lasting for hours. The female laid
one hundred and twenty-four eggs within twenty-five days.

The eggs hatched after eight days, under favorable conditions,
such as those under which the female was kept. They did not
hatch in the cold. Eggs kept near the person during the day and
hung in clothing by the bedside at night, during the winter, in a cold
room, did not hatch until the thirty-fifth day. When the nymphs
emerge from the eggs, they feed at once, if given a chance to do so.
They are prone to scatter about the person and abandon the frag¬
ment of cloth to which the adult clings.

Pediculus Corporis

The adult stage is reached on the eleventh day, after three molts,
about four days apart. Adults enter into copulation about the
fifth day and as the eggs require eight days for development,
the total cycle, under favorable conditions, is about twenty-
four days. Warburton’s data differ considerably from those com¬
monly quoted and serve to emphasize the necessity for detailed studies
of some of the commonest of parasitic insects.

Body lice are voracious feeders, producing by their bites and the
irritating saliva which they inject, rosy elevations and papules which
become covered with a brownish
crust. The intense itching pro¬
vokes scratching, and character¬
istic white scars (fig. 67) sur¬
rounded by brownish pigment
(fig. 68) are formed. The skin
may become thickened and take
on a bronze tinge. This mela¬
noderma is especially marked
in the region between the shoul¬
ders but it may become genera¬
lized, a prominent characteristic
of “vagabond’s disease.” Ac¬
cording to Dubre and Beille,
this melanoderma is due to a
toxic substance secreted by the
lice, which indirectly provokes
the formation of pigment.

Control measures, in the case
of the body louse, consist in
boiling or steaming the clothes or in some cases, sterilizing by dry heat.
The dermatitis may be relieved by the use of zinc-oxide ointment,
to which Pusey recommends that there be added, on account of their
parasiticidal properties, sulphur and balsam of Peru, equal parts, 15
to 30 grains to the ounce.

Phthirius pubis (= P. inguinalis ), the pubic louse, or so-called
“crab louse,” differs greatly from the preceding in appearance. It is
characterized by its relatively short head which fits into a broad
depression in the thorax. The latter is broad and flat and merges
into the abdomen. The first pair of legs is slender and terminated
by a straight claw. The second and third pairs of legs are thicker

67. Pediculosis in man caused by the body
louse. After Morrow.

Parasitic Arthropods

and are provided with powerful claws fitted for clinging to hairs.
The females (fig. 69) measure 1.5 to 2 mm. in length by 1.5 mm. in

breadth. The male averages a
little over half as large. The eggs,
or nits, are fixed at the base of the
hairs. Only a few, ten to fifteen
are deposited by a single female,
and they hatch in about a week’s
time. The young lice mature in
two weeks.

The pubic louse usually infests
the hairs of the pubis and the
perineal region. It may pass to
the arm pits or even to the beard
or moustache. Rarely, it occurs
on the eyelids, and it has even
been found, in a very few instances,
occurring in all stages, on the scalp.
Infestation may be contracted
from beds or even from badly in¬
fested persons in a crowd. We
have seen several cases which un¬
doubtedly were due to the use of
public water closets. It produces
papular eruption and an intense
pruritis. When abundant, there
occurs a grayish discoloration of
the skin which Duguet has shown
is due to a poisonous saliva injected by the louse,
as is the melanoderma caused by the body louse.

The pubic louse may be exterminated by the <5 ~' ~~~
measures recommended for the head louse, or / ///
by the use of officinal mercurial ointment.

68. Melanoderma caused by the body
louse. From Portfolio of Dermo-
chromes. by permission of Rebman
& Co., New York, Publishers.

IIemiptera

Several species of Hemiptera-Heteroptera are 69 Phthirius pubi ,. Ven _
habitual parasites of man, and others occur jv'iof pect of ^ emalc -
as occasional or accidental parasites. Of all

these, the most important and widespread are the bed-bugs, belong¬
ing to the genus Cimex (= Acanthia).

The Bed-hugs

The Bed-bugs—The bed-bugs are characterized by a much flat¬
tened oval body, with the short, broad head unconstricted behind,
and fitting into the strongly excavated anterior margin of the thorax.
The compound eyes are prominent, simple eyes lacking. Antennae
four-jointed, the first segment short, the second long and thick, and
the third and fourth slender. The tarsi are short and three seg¬
mented.

It is often assumed in the literature of the subject that there is
but a single species of Cimex attacking man, but several such species
are to be recognized. These are distinguishable by the characters

given in Chapter XII. We shall con¬
sider especially Cimex lectularius, the
most common and widespread species.

Cimex lectularius (= Acanthia
lectularia, Clinocoris lectularius), is
one of the most cosmopolitan of human
parasites but, like the lice, it has been
comparatively little studied until
recent years, when the possibility
that it may be concerned with the
transmission of various diseases has
awakened interest in the details of
its life-history and habits.

The adult insect (fig 70) is 4-5
mm. long by 3 mm. broad, reddish
brown in color, with the beak and body appendages lighter in color.
The short, broad and somewhat rectangular head has no neck-like
constriction but fits into the broadly semilunar prothorax. The
four segmented labium or proboscis encloses the lancet-like maxillae
and mandibles. The distal of the four antennal segments is slightly
club-shaped. The prothorax is characteristic of the species, being
deeply incised anteriorly and with its thin lateral margins somewhat
turned up. The mesothorax is triangular, with the apex posteriorly,
and bears the greatly atrophied first pair of wings. There is no trace
of the metathoracic pair. The greatly flattened abdomen has eight
visible segments, though in reality the first is greatly reduced and
has been disregarded by most writers. The body is densely covered
with short bristles and hairs, the former being peculiarly saber¬
shaped structures sharply toothed at the apex and along the convex
side (fig. 1596).

70. Cimex lectularius adult and eggs.
Photograph by M. V. S.

Parasitic Arthropods

The peculiar disagreeable odor of the adult bed-bug is due to the
secretion of the stink glands which lie on the inner surface of the
mesostemum and open by a pair of orifices in front of the metacoxae,
near the middle line. In the nymphs, the thoracic glands are not
developed but in the abdomen there are to be found three unpaired
dorsal stink glands, which persist until the fifth molt, when they
become atrophied and replaced by the thoracic glands. The nymphal
glands occupy the median dorsal portion of the abdomen, opening
by paired pores at the anterior margin of the fourth, fifth and sixth
segments. The secretion is a clear, oily, volatile fluid, strongly acid
in reaction. Similar glands are to be found in most of the Hemiptera-
Heteroptera and their secretion is doubtless protective, through
being disagreeable to the birds. In the bed-bug, as Marlatt points
out, “it is probably an illustration of a very common phenomenon
among animals, i. e., the persistence of a characteristic which is no
longer of any special value to the possessor.’’ In fact, its possession
is a distinct disadvantage to the bed-bug, as the odor frequently
reveals the presence of the bugs, before they are seen.

The eggs of the bed-bug (fig. 70) are pearly white, oval in out¬
line, about a millimeter long, and possess a small operculum or cap
at one end, which is pushed off when the young hatches. They are
laid intermittently, for a long period, in cracks and crevices of beds
and furniture, under seams of mattresses, under loose wall paper,
and similar places of concealment of the adult bugs. Girault (1905)
observed a well-fed female deposit one hundred and eleven eggs
during the sixty-one days that she was kept in captivity. She had
apparently deposited some of her eggs before being captured.

The eggs hatch in six to ten days, the newly emerged nymphs
being about 1.5 mm. in length and of a pale yellowish white color.
They grow slowly, molting five times. At the last molt the mesa-
thoracic wing pads appear, characteristic of the adult. The total
length of the nymphal stage varies greatly, depending upon condi¬
tions of food supply, temperature and possibly other factors. Mar¬
latt (1907) found under most favorable conditions a period averaging
eight days between molting which, added to an equal egg period,
gave a total of about seven weeks from egg to adult insect. Girault
(1912) found the postembryonic period as low as twenty-nine days
and as high as seventy days under apparently similar and normal
conditions of food supply. Under optimum and normal conditions
of food supply, beginning August 27, the average nymphal life was

The Bed-bugs

69.9 days; average number of meals 8.75 and the molts 5. Under
conditions allowing about half the normal food supply the average
nymphal life was from 116.9 to 139 days. Nymphs starved from
birth lived up to 42 days. We have kept unfed nymphs, of the first
stage, alive in a bottle for 75 days. The interesting fact was brought
out that under these conditions of minimum food supply there were
sometimes six molts instead of the normal number.

The adults are remarkable for their longevity, a factor which is
of importance in considering the spread of the insect and methods of
control. Dufour (1833) (not De Geer, as often stated) kept speci¬
mens for a year, in a closed vial, without food. This ability, coupled
with their willingness to feed upon mice, bats, and other small mam¬
mals, and even upon birds, accounts for the long periods that deserted
houses and camps may remain infested. There is no evidence that
under such conditions they are able to subsist on the starch of the
wall paper, juices of moistened wood, or the moisture in the accumu¬
lations of dust, as is often stated.

There are three or four generations a year, as Girault’s breeding
experiments have conclusively shown. He found that the bed-bug
does not hibernate where the conditions are such as to allow it to
breed and that breeding is continuous unless interrupted by the lack
of food or, during the winter, by low temperature.

Bed-bugs ordinarily crawl from their hiding places and attack
the face and neck or uncovered parts of the legs and arms of their
victims. If undisturbed, they will feed to repletion. We have
found that the young nymph would glut itself in about six minutes,
though some individuals fed continuously for nine minutes, while
the adult required ten to fifteen minutes for a full meal. When
gorged, it quickly retreats to a crack or crevice to digest its meal,
a process which requires two or three days. The effect of the bite
depends very greatly on the susceptibility of the individual attacked.
Some persons are so little affected that they may be wholly ignorant
of the presence of a large number of bugs. Usually the bite produces
a small hard swelling, or wheal, whitish in color. It may even be
accompanied by an edema and a disagreeable inflammation, and in
such susceptible individuals the restlessness and loss of sleep due to
the presence of the insects may be a matter of considerable im¬
portance. Stiles (1907) records the case of a young man who under¬
went treatment for neurasthenia, the diagnosis being agreed upon by
several prominent physicians; all symptoms promptly disappeared,

Parasitic Arthropods

however, immediately following a thorough fumigation of his rooms,
where nearly a pint of bed-bugs were collected.

It is natural to suppose that an insect which throughout its whole-
life is in such intimate relationship with man should play an important
r 61 e in the transmission of disease. Yet comparatively little is-,
definitely known regarding the importance of the bed-bug in this,
respect. It has been shown that it is capable of transmitting the
bubonic plague, and South American trypanosomiasis. Nuttall
succeeded in transmitting European relapsing fever from mouse to-
mouse by its bite. It has been claimed that Oriental sore, tubercu¬
losis, and even syphilis may be so carried. These phases of the
subject will be considered later.

The sources of infestation are many, and the invasion of a house
is not necessarily due to neglect, though the continued presence of
the pests is quite another matter. In apartments and closely placed
houses they are known to invade new quarters by migration. They
are frequently to be met with in boat and sleeper berths, and even
the plush seats of day coaches, whence a nucleus may be carried in
baggage to residences. They may be brought in the laundry or
in clothes of servants.

Usually they are a great scourge in frontier settlements and it is.
generally believed that they live in nature under the bark of trees,
in lumber, and under similar conditions. This belief is founded upon
the common occurrence of bugs resembling the bed-bug, in such
places. As a matter of fact, they are no relation to bed-bugs but
belong to plant-feeding forms alone (fig. 19 c, d).

It is also often stated that bed-bugs live in poultry houses, in
swallows nests, and on bats, and that it is from these sources that they
gain access to dwellings. These bugs are specifically distinct from
the true bed-bug, but any of them may, rarely, invade houses.
Moreover, chicken houses are sometimes thoroughly infested with
the true Cimex lectularius.

Control measures consist in the use of iron bedsteads and the
reduction of hiding places for the bugs. If the infestation is slight
they may be exterminated by a vigilant and systematic hunt, and
by squirting gasoline or alcohol into cracks and crevices of the beds,
and furniture. Fumigation must be resorted to in more general
infestations.

The simplest and safest method of fumigation is by the use of
flowers of sulphur at the rate of two pounds to each one thousand

The Bed-hugs

cubic feet of room space. The sulphur should be placed in a pan,
a well made in the top of the pile and a little alcohol poured in, to
facilitate burning. The whole should be placed in a larger pan
and surrounded by water so as to avoid all danger of fire. Windows
should be tightly closed, beds, closets and drawers opened, and
bedding spread out over chairs in order to expose them fully to the
fumes. As metal is tarnished by the sulphur fumes, ornaments,
clocks, instruments, and the like should be removed. When all is
ready the sulphur should be fired, the room tightly closed and left
for twelve to twenty-four hours. Still more efficient in large houses,
or where many hiding places favor the bugs, is fumigation with
hydrocyanic acid gas. This is a deadly poison and must be used
under rigid precautions. Through the courtesy of Professor Herrick,
who has had much experience with this method, we give in the Ap¬
pendix, the clear and detailed directions taken from his bulletin on
“Household Insects.”

Fumigation with formaldehyde gas, either from the liquid or
“solid” formalin, so efficient in the case of contagious diseases, is
useless against bed-bugs and most other insects.

Other Bed-bugs — Cimex hemipterus (= C. rotundatus ) is a trop¬
ical and subtropical species, occurring in both the old and new world.
Patton and Cragg state that it is distributed throughout India,
Burma, Assam, the Malay Peninsula, Aden, the Island of Mauri¬
tius, Reunion, St. Vincent and Porto Rico. “It is wddely distribu¬
ted in Africa, and is probably the common species associated there
with man.” Brumpt also records it for Cuba, the Antilles, Brazil,
and Venezuela.

This species, which is sometimes called the Indian bed-bug,
differs from C. lectularius in being darker and in having a more
elongate abdomen. The head also is shorter and narrower, and the
prothorax has rounded borders.

It has the same habits and practically the same life cycle as
Cimex lectularius. Mackie, in India, has found that it is capable
of transmitting the Asiatic type of recurrent fever. Roger suggested
that it was also capable of transmitting kala-azar and Patton has
described in detail the developmental stages of Leishmania, the
causative organism of Kala-azar, in the stomach of this bug, but
Brumpt declares that the forms described are those of a common,
non-pathogenic flagellate to be found in the bug, and have nothing

Parasitic Arthropoda

to do with the human disease. Brumpt has shown experimentally
that Cimex hemipterus may transmit Trypanosoma cruzi in its excre¬
ment.

Cimex boueti, occurring in French Guinea, is another species
attacking man. Its habits and general life history are the same as
for the above species. It is 3 to 4.5 mm. in length,
has vestigial elytra, and much elongated antennae and
legs. The extended hind legs are about as long as the
body.

Cimex columbarius, a widely distributed species nor¬
mally living in poultry houses and dovecotes, C.inodorus,
infesting poultry in Mexico, C. hirundinis, occurring in
the nests of swallows in Europe and Oeciacus vicarius
(fig. 1 gi) occurring in swallow’s nests in this country,
sangu°isugus nus are species which occasionally infest houses and attack
man.

Conorhinus sanguisugus , the cone-nosed bed-bug. We have seen
in our consideration of poisonous insects, that various species of
Reduviid bugs readily attack man. Certain of these are nocturnal
and are so commonly found in houses that they have gained the
name, of “big bed-bugs.” The most noted of these, in the United
States, is Conorhinus sangiusugus (fig. 71), which is widely dis¬
tributed in our Southern States.

Like its near relatives, Conorhinus
sangiusugus is carnivorous in habit and
feeds upon insects as well as upon
mammalian and human blood. It is
reported as often occurring in poultry
houses and as attacking horses in
barns. The life history has been
worked out in considerable detail by
Marlatt, (1902), from whose account we
extract the following.

The eggs are white, changing to
yellow and pink before hatching. The
young hatch within twenty days
and there arc four nymphal stages.

In all these stages the insect is active and predaceous, the mouth-
parts (fig. 72) being powerfully developed. The eggs are normally
deposited, and the early stages are undoubtedly passed, out of doors,

72. Beak of Conorhinus sanguisugus.
After Marlatt.

Cone-nosed, Bugs

the food of the immature forms being other insects. Immature
specimens are rarely found indoors. It winters both in the partly
grown and adult stage, often under the bark of trees or in any
similar protection, and only in its nocturnal spring and early
summer flights does it attack men. Marlatt states that this insect
seems to be decidedly on the increase in the region which it parti¬
cularly infests, — the plains region from Texas northward and west¬
ward. In California a closely related species of similar habits is
known locally as the “monitor bug.”

The effect of the bite of the giant bed-bug on man is often very
severe, a poisonous saliva apparently being injected into the wound.
We have discussed this phase of the subject more fully under the
head of poisonous insects.

Conorhinus megistus is a Brazilian species very commonly attack¬
ing man, and of special interest since Chagas has shown that it is
the carrier of a trypanosomiasis of man. Its habits and life history
have been studied in detail by Neiva, (1910).

This species is now pre-eminent'ly a household insect, depositing
its eggs in cracks and crevices in houses, though this is a relatively
recent adaptation. The nymphs emerge in from twenty to forty
days, depending upon the temperature. There are five nvmphal
stages, and as in the case of true bed-bugs, the duration of these is
very greatly influenced by the availability of food and by tempera¬
ture. Neiva reckons the entire life cycle, from egg to egg, as requir¬
ing a minimum of three hundred and twenty -four days.

The nymphs begin to suck blood in three to five days after hatch¬
ing. They usually feed at night and m the dark, attacking especially
the face of sleeping individuals. The bite occasions but little pain.
The immature insects live in cracks and crevices in houses and
invade the beds which are in contact with walls, but the adults are
active flyers and attack people sleeping in hammocks. The males
as well as the females are blood suckers.

Like many blood-sucking forms, Conorhinus megistus can endure
for long periods without food. Neiva received a female specimen
which had been for fifty-seven days alive in a tightly closed box.
They rarely feed on two consecutive days, even on small quantities
of blood, and were never seen to feed on three consecutive days.

Methods of control consist in screening against the adult bugs,
and the elimination of crevices and such hiding places of the nymphs.
Where the infestation is considerable, fumigation with sulphur is
advisable.

94 Parasitic Arthropoda

Parasitic Diptera or Flies

Of the Diptera or two-winged flies, many species occasionally
attack man. Of these, a few are outstanding pests, many of them
may also serve to disseminate disease, a phase of our subject which
will be considered later. We shall now consider the most important
of the group from the viewpoint of their direct attacks on man.

Psychodidae or Moth-Flies

The Psychodidae or Moth-flies, include a few species which attack
man, and at least one species, Phlebotomus papatasii, is known
to transmit the so-called “three-day fever” of man. Another species
is supposed to be the vector of Peruvian verruga.

The family is made up of small, sometimes very small, nematocer-
ous Diptera, which are densely covered with hairs, giving them a
moth-like appearance. The wings are relatively large, oval or
lanceolate in shape, and when at rest are held in a sloping manner
over the abdomen, or are held horizontally in such a way as to give
the insect a triangular outline. Not only is the moth-like appearance
characteristic, but the venation of the wings (fig. 163, d) is very peculiar
and, according to Comstock, presents an extremely generalized form.
All of the longitudinal veins separate near the base of the wing
except veins R 2 and R 3 and veins Mi and M 2 . Cross veins are
wanting in most cases.

Comparatively little is known regarding the life-history and
habits of the Psychodidae, but one genus, Phlebotomus, contains
minute, blood-sucking species, commonly known as sand-flies. The
family is divided into two subfamilies, the Psychodinae and the
Phlebotominae. The second of these, the Phlebotominae, is of
interest to us.

The Phlebotominae — The Phlebotominae differ from the Psychod¬
inae in that the radical sector branches well out into the wing rather
than at the base of the wing. They are usually less hairy than the
Psychodinae. The ovipositor is hidden and less strongly chitinized.
The species attacking man belong to the genus Phlebotomus , small
forms with relatively large, hairy wings which are held upright,
and with elongate proboscis. The mandibles and maxillae are ser¬
rated and fitted for biting.

According to Miss Summers (1913) there are twenty-nine known
species of the genus Phlebotomus, five European, eleven Asiatic,

Phlebotomus Flies

seven African and six American. One species only, Phlebotomus
vexator, has been reported for the United States. This was described
by Coquillett, (1907), from species taken on Plummer’s Island, Mary¬
land. It measures only 1.5 mm. in length. As it is very probable
that this species is much more widely distributed, and that other
species of these minute flies will be found to occur in our fauna, we
quote Coquillett’s description.

Phlebotomus vexator, Coq.: Yellow, the mesonotum brown,
hairs chiefly brown; legs in certain lights appear brown, but are
covered with a white tomentum; wings hyaline, unmarked; the first
vein (Ri) terminates opposite one-fifth of the length- of the first
submarginal cell (cell R 2 ); this cell is slightly over twice as long
as its petiole; terminal, horny portion of male claspers slender,
bearing many long hairs; the apex terminated by two curved spines
which are more than one-half as long as the preceding part, and just
in front of these are two similar spines, while near the middle of the
length of this portion is a fifth spine similar to the others. Length
1.5 mm.

The life-history of the Phlebotomus flies has been best worked out
for the European Phlebotomus papatasii and we shall briefly sum¬
marize the account of Doerr and Russ (1913) based primarily on work
on this species. The European Phlebotomus flies appear at the
beginning of the warm season, a few weeks after the cessation of the
heavy rains and storms of springtime. They gradually become more
abundant until they reach their first maximum, which in Italy is near
the end of July (Grassi). They then become scarcer but reach a
•second maximum in September. At the beginning of winter they
vanish completely, hibernating individuals not being found.

After fertilization there is a period of eight to ten days before ovi-
position. The eggs are then deposited, the majority in a single mass
covered by a slimy secretion from the sebaceous glands. The larvae
emerge in fourteen to twenty days. There is uncertainty as to the
length of larval life, specimens kept in captivity remaining fifty or
more days without transforming. Growth may be much more rapid
in nature. The larvae do not live in fluid media but in moist detritus
in dark places. Marett believes that they live chiefly on the excre¬
ment of pill-bugs (Oniscidae) and lizards. Pupation always occurs
during the night. The remnants of the larval skin remain attached
to the last two segments of the quiescent pupa and serve to attach
it to the stone on which it lives. The pupal stage lasts eleven to
sixteen days, the adult escaping at night.

Parasitic Arthropoda

Only the females suck blood. They attack not only man but all
warm-blooded animals and, according to recent workers, also cold¬
blooded forms, such as frogs, lizards, and larvae. Indeed, Townsend
(1914) believes that there is an intimate relation between Phlebotomus
and lizards, or other reptiles the world over. The Phlebotomus
passes the daylight hours within the darkened recesses of the loose
stone walls and piles of rock in order to escape wind and strong light.
Lizards inhabit the same places, and the flies, always ready to suck
blood in the absence of light and wind, have been found more prone
to suck reptilian than mammalian blood.

On hot summer nights, when the wind is not stirring, the Phleboto¬
mus flies, or sand-flies, as they are popularly called, invade houses and
sleeping rooms in swarms and attack the inmates. As soon as light
begins to break the flies either escape to the breeding places, or cool,
dark places protected from the wind, or a part of them remain in the
rooms, hiding behind pictures, under garments, and in similar places.
Wherever the Phlebotomus flies occur they are an intolerable nui¬
sance. On account of their small size they can easily pass through
the meshes of ordinary screens and mosquito curtains. They attack
silently and inflict a very painful, stinging bite, followed by itching.
The ankles, dorsum of the feet, wrists, inner elbow, knee joint and
similar places are favorite places of attack, possibly on account of
their more delicate skin.

Special interest has been attracted to these little pests in recent
years, since it has been shown that they transmit the European
“pappatici fever” or “three day fever.” More recently yet, it
appears that they are the carriers of the virus of the Peruvian “ver¬
ruga.” This phase of the subject will be discussed later.

Control measures have not been worked out. As Newstead says,
“ I11 consideration of the facts which have so far been brought to light
regarding the economy of Phlebotomus, it is clearly evident that the
task of suppressing these insects is an almost insurmountable one.
Had we to deal with insects as large and as accessible as mosquitoes,
the adoption of prophylactic measures would be comparatively easy,
but owing to the extremely minute size and almost flea-like habits of
the adult insects, and the enormous area over which the breeding-
places may occur, we are faced with a problem which is most difficult
of solution.” For these reasons, Newstead considers that the only
really prophylactic measures which can at present be taken, are those
which are considered as precautionary against the bites of the insects.

Culcidce, or Mosquitoes 97

Of repellents, he cites as one of the best a salve composed of the
following:

01 . Anisi . 3 grs.

01 . Eucalypti . 3 grs.

01 . Terebenth . 3 grs.

Unq. Acid Borac.

Of sprays he recommends as the least objectionable and at the
same time one of the most effective, formalin. “The dark portions
and angles of sleeping apartments should be sprayed with a one per
cent, solution of this substance every day during the season in which
the flies are prevalent. A fine spraying apparatus is necessary for
its application and an excessive amount must not be applied. It is
considered an excellent plan also to spray the mosquito curtains
regularly every day towards sunset; nets thus treated are claimed to
repel the attacks of these insects.” This effectiveness of formalin is
very surprising for, as we have seen, it is almost wholly ineffective
against bed-bugs, mosquitoes, house flies and other insects, where it
has been tried.

A measure which promises to be very effective, where it can be
adopted, is the use of electric fans so placed as to produce a current
of air in the direction of the windows of sleeping apartments. On
account of the inability of the Phlebotomus flies to withstand even
slight breezes, it seems very probable that they would be unable to
enter a room so protected.

Culicidae or Mosquitoes

From the medical viewpoint, probably the most interesting and
important of the blood-sucking insects are the mosquitoes. Certainly
this is true of temperate zones, such as those of the United States.
The result is that no other group of insects has aroused such wide¬
spread interest, or has been subjected to more detailed study than
have the mosquitoes, since their role as carriers of disease was made
known. There is an enormous literature dealing with the group, but
fortunately for the general student, this has been well summarized
by a number of workers. The most important and helpful of the
general works are those of Howard (1901), Smith (1904), Blanchard
(1905), Mitchell (1907), and especially of Howard, Dyar, and Knab,
whose magnificent monograph is still in course of publication.

Parasitic Arthropoda

Aside from their importance as carriers of disease, mosquitoes are
notorious as pests of man, and the earlier literature on the group is
largely devoted to references to their enormous numbers and their
blood-thirstiness in certain regions. They are to be found in all
parts of the world, from the equator to the Arctic and Antarctic
regions. Linnaeus, in the “Flora Lapponica,” according to Howard,
Dyar and Knab, “dwells at some length upon the great abundance of
mosquitoes in Lapland and the torments they inflicted upon man and
beast. He states that he believes that nowhere else on earth are they
found in such abundance and he compares their numbers to the dust
of the earth. Even in the open, you cannot draw your breath without
having your mouth and nostrils filled with them; and ointments of
tar and cream or of fish grease are scarcely sufficient to protect even
the case-hardened cuticle of the Laplander from their bite. Even in
their cabins, the natives cannot take a mouthful of food or lie down
to sleep unless they are fumigated almost to suffocation.” In some
parts of the Northwestern and Southwestern United States it is
necessary to protect horses working in the fields by the use of sheets or
burlaps, against the ferocious attacks of these insects. It is a sur¬
prising fact that even in the dry deserts of the western United States
they sometimes occur in enormous numbers.

Until comparatively recent years, but few species of mosquitoes
were known and most of the statements regarding their life-history
were based upon the classic work of Reaumur (1738) on the biology
of the rain barrel mosquito, Culex pipiens. In 1896, Dr. Howard
refers to twenty-one species in the United States, now over fifty are
known; Giles, in 1900, gives a total of two hundred and forty-two
for the world fauna, now over seven hundred species are known.
We have found eighteen species at Ithaca, N. Y.

All of the known species of mosquitoes are aquatic in the larval
stage, but in their life-histories and habits such great differences occur
that we now know that it is not possible to select any one species as
typical of the group. For our present purpose we shall first discuss
the general characteristics and structure of mosquitoes, and shall
then give the life-history of a common species, following this by a
brief consideration of some of the more striking departures from what
have been supposed to be the typical condition.

The Culicidse are slender, nematocerous I ffptcra with narrow wings,
antennae plumose in the males, and usually with the proboscis much
longer than the head, slender, firm and adapted for piercing in the

Culicidce, or Mosquitoes

female. The most characteristic feature is that the margins of the
wings and, in most cases, the wing veins possess a fringe of scale-like
hairs. These may also cover in part, or entirely, the head, thorax,
abdomen and legs. The females, only, suck blood.

On account of the importance of the group in this country and the
desirability of the student being able to determine material in various
stages, we show in the accompanying figures the characters most
used in classification.

The larvae (fig. 73) are elongate,
with the head and thorax sharply
distinct. The larval antennae are
prominent, consisting of a single
cylindrical and sometimes curved
segment. The outer third is often
narrower and bears at its base a
fan-shaped tuft of hairs, the ar¬
rangement and abundance of which
is of systematic importance. About
the mouth are the so-called rotary
mouth brushes, dense masses of
long hairs borne by the labrum
and having the function of sweep¬
ing food into the mouth. The

, , , fatral brush $.(5

form and arrangement or thoracic, <,/ dm

abdominal, and anal tufts of hair anal .../fgplf

vary in different species and present ‘ J ' IL /// DonaJ. tufa

characteristics of value. On either / 7 I

side of the eighth abdominal seg- 73 - Ct ^ucture showing details of external

ment is a patch of scales varying

greatly in arrangement and number and of much value in separating
species. Respiration is by means of tracheae which open at the apex
of the so-called anal siphon, when it is present. In addition, there
are also one or two pairs of tracheal gills which vary much in appear¬
ance in different species. On the ventral side of the anal siphon is a
double row of flattened, toothed spines whose number and shape are
likewise of some value in separating species. They constitute the
comb or pecten.

The pupa (fig. 139,b) unlike that of most insects, is active, though it
takes no food. The head and thorax are not distinctly separated, but
the slender flexible abdomen in sharply marked off. The antennae,

dnk.il rial
tuft-,

1 \ Pltuth brush •

dnknna

IOO

Parasitic Arthropoda

mouth-parts, legs, and wings of the future adult are now external, but
enclosed in chitinous cases. On the upper surface, near the base of
the wings are two trumpets, or breathing tubes, for the pupal spiracles
are towards the anterior end instead of at the caudal end, as in the
larva. At the tip of the abdomen is a pair of large chitinous swim¬
ming paddles.

As illustrative of the life cycle of a mosquito we shall discuss the
development of a common house mosquito, Culex pipiens, often
referred to in the Northern United States as the rain barrel mosquito.
Its life cycle is often given as typical for the entire group, but, as we
have already emphasized, no one species can serve this purpose.

The adults of Culex pipiens hibernate throughout the winter in
cellars, buildings, hollow trees, or similar dark shelters. Early in
the spring they emerge and deposit their eggs in a raft-like mass.
The number of eggs in a single mass is in the neighborhood of two
hundred, recorded counts varying considerably. A single female
may deposit several masses during her life time. The duration of
the egg stage is dependent upon temperature. In the warm summer
time the larvae may emerge within a day. The larvae undergo four
molts and under optimum conditions may transform into pups in
about a week’s time. Under the same favorable conditions, the pupal
stage may be completed in a day’s time. The total life cycle of Culex
pipiens, under optimum conditions, may thus be completed in a week
to ten days. This period may be considerably extended under less
favorable conditions of temperature and food supply.

Culex pipiens breeds continuously throughout the summer,
developing in rain barrels, horse troughs, tin cans, or indeed, in any
standing water about houses, which lasts for a week or more. The
catch basins of sewers furnish an abundant supply of the pests under
some conditions. Such places, the tin gutters on residences, and all
possible breeding places must be considered in attempts to extermi¬
nate this species.

Other species of mosquitoes may exhibit radical departures from
Culex pipiens in life-history and habits. To control them it is essen¬
tial that the biological details be thoroughly worked out for, as
Howard, Dyar, and Knab have emphasized, “much useless labor and
expense can be avoided by an accurate knowledge of the habits of the
species.” For a critical discussion of the known facts the reader is
referred to their monograph. We shall confine ourselves to a few
illustrations.

Culicidce, or Mosquitoes

IOI

The majority of mosquitoes in temperate climates hibernate in
the egg stage, hatching in the spring or even mild winter days in water
from melting snow. It is such single-brooded species which appear in
astounding numbers in the far North. Similarly, in dry regions the
eggs may stand thorough dessication, and yet hatch out with great
promptness when submerged by the rains. “Another provision to
insure the species against destruction in such a case, exists in the fact
* * * that not all the eggs hatch, a part of them lying over until

again submerged by subsequent rains.’’ In temperate North
America, a few species pass the winter in the larval state. An inter¬
esting illustration of this is afforded by Wyeomia smithii, whose
larvae live in pitcher plants and are to be found on the coldest winter
days imbedded in the solid ice. Late in the spring, the adults emerge
and produce several broods during the summer.

In the United States, one of the most important facts which has
been brought out by the intensive studies of recent years is that cer¬
tain species are migratory and that they can travel long distances and
become an intolerable pest many miles from their breeding places.
This was forcibly emphasized in Dr. Smith’s work in New Jersey,
when he found that migratory mosquitoes, developing in the salt
marshes along the coast, are the dominant species largely responsible
for the fame of the New Jersey mosquito. The species concerned are
Aedes sollicitans, A. cantator and A. tceniorhynchus. Dr. Smith
decided that the first of these might migrate at least forty miles
inland. It is obvious that where such species are the dominant pest,
local control measures are a useless waste of time and money. Such
migratory habits are rare, however, and it is probable that the
majority of mosquitoes do not fly any great distance from their
breeding places.

While mosquitoes are thought of primarily as a pest of man, there
are many species which have never been known to feed upon human
or mammalian blood, no matter how favorable the opportunity.
According to Howard, Dyar, and Knab, this is true of Culex territans,
one of the common mosquitoes in the summer months in the Northern
United States. There are some species, probably many, in which
the females, like the males, are plant feeders. In experimental work,
both sexes are often kept alive for long periods by feeding them upon
ripe banana, dried fig, raisins, and the like, and in spite of sweeping
assertions that mosquitoes must have a meal of blood in order to
stimulate the ovaries to development, some of the common blood-

102

Parasitic Arthropoda

sucking species, notably Culex pipiens, have been bred repeatedly
without opportunity to feed upon blood.

The effect of the bite varies greatly with different species and
depends upon the susceptibility of the individual bitten. Some
persons are driven almost frantic by the attacks of the pests when
their companions seem almost unconscious of any inconvenience..
Usually, irritation and some degree of inflammation appear shortly
following the bite. Not infrequently a hardened wheal or even a.
nodule forms, and sometimes scratching leads to secondary infection
and serious results.

The source of the poison is usually supposed to be the salivary
glands of the insect. As we have already pointed out, (p. 34) r
Macloskie believed that one lobe of the gland, on each side, was;
specialized for forming the poison, while a radically different view is.
that of Schaudinn, who believed that the irritation is due to the-
expelled contents of the oesophageal diverticula, which contain a.
gas and a peculiar type of fungi or bacteria. In numerous attempts,
Schaudinn was unable to produce any irritation by applying the
triturated salivary glands to a wound, but obtained the typical result,
when he used the isolated diverticula.

The irritation of the bite may be relieved to some extent by using
ammonia water, a one per cent, alcoholic solution of menthol, or
preparations of cresol, or carbolic acid. Dr. Howard recommends
rubbing the bite gently with a piece of moist toilet soap. Castellani
and Chalmers recommend cleansing inflamed bites with one in forty
carbolic lotion, followed by dressing with boracic ointment. Of
course, scratching should be avoided as much as possible.

Repellents of various kinds are used, for warding off the attacks
of the insects. We have often used a mixture of equal parts of oil
of pennyroyal and kerosene, applied to the hands and face. Oil of
citronella is much used and is less objectionable to some persons. A
recommended formula is, oil of citronella one ounce, spirits of camphor
one ounce, oil of cedar one-half ounce. A last resort would seem to-
be the following mixture recommended by Howard, Dyar, and Knab
for use by hunters and fishermen in badly infested regions, against
mosquitoes and blackflies.

Take 2]/^ lbs. of mutton tallow and strain it. While still hot add
]/2 lb. black tar (Canadian tar). Stir thoroughly and pour into the-
receptacle in which it is to be contained. When nearly cool stir in
three ounces of oil of citronella and 1)4 oz. of pennyroyal.

Culicidce , or Mosquitoes

103

At night the surest protection is a good bed net. There are many
types of these in use, but in order to be serviceable and at the same
time comfortable it should be roomy and hung in such a way as to
be stretched tightly in every direction. We prefer one suspended
from a broad, square frame, supported by a right-angled standard
which is fastened to the head of the bed. It must be absolutely free
from rents or holes and tucked in securely under the mattress or it
will serve merely as a convenient cage to retain mosquitoes which gain
an entrance. While such nets are a convenience in any mosquito
riden community, they are essential in regions where disease-carrying
species abound. Screening of doors, windows and porches, against
the pests is so commonly practiced in this country that its importance
and convenience need hardly be urged.

Destruction of mosquitoes and prevention of breeding are of
fundamental importance. Such measures demand first, as we have
seen, the correct determination of the species which is to be dealt
with, and a knowledge of its life-history and habits. If it prove to be
one of the migratory forms, it is beyond mere local effort and becomes
a problem demanding careful organization and state control. An
excellent illustration of the importance and effectiveness of work
along these lines is afforded by that in New Jersey, begun by the late
Dr. John B. Smith and being pushed with vigor by his successor,
Dr. Headlee.

In any case, there is necessity for community action. Even near
the coast, where the migratory species are dominant, there are the
local species which demand attention and which cannot be reached
by any measures directed against the species of the salt marshes. The
most important of local measures consist in the destruction of breed¬
ing places by filling or draining ponds and pools, clearing up of more
temporary breeding places, such as cans, pails, water barrels and the
like. Under conditions where complete drainage of swamps is im¬
practicable or undesirable, judicious dredging may result in a pool or
series of steep-sided pools deep enough to maintain a supply of fish,
which will keep down the mosquito larvae. Where water receptacles
are needed for storage of rain water, they should be protected by
careful screening or a film of kerosene over the top of the water,
renewed every two weeks or so, so as to prevent mosquitoes from
depositing their eggs. When kerosene is used, water drawn from the
bottom of the receptacle will not be contaminated by it to any in¬
jurious extent. Where ponds cannot be drained much good will be

104

Parasitic Arthropoda

accomplished by spraying kerosene oil on the surface of the water, or
by the introduction of fish which will feed on the larvas.

Detailed consideration of the
most efficient measures for con¬
trolling mosquitoes is to be found
in Dr. Howard’s Bulletin No. 88
of the Bureau of Entomology,
“Preventive and remedial work
against mosquitoes” or, in more
summarized form, in Farmers’
Bulletin No. 444. One of these
should be obtained by any person
interested in the problems of mos¬
quito control and public health.

The Simuliidae, or Black Flies

The Simuliidae, or black flies, are small, dark, or black flies, with
a stout body and a hump-back appearance. The
antennae are short but eleven-segmented, the wings
broad, without scales or hairs, and with the anterior
veins stout but the others very weak. The mouth-
parts (fig. 74) are fitted for biting.

The larvae of the Simuliidae (fig. 75) are aquatic
and, unlike those of mosquitoes, require a well aerated,
or swiftly running water. Here they attach to stones,
logs, or vegetation and feed upon various micro¬
organisms. They pupate in silken cocoons open at
the top. Detailed life-histories have not been worked
out for most of the species. We shall consider as
typical that of Simulium pictipes, an inoffensive
species widely distributed in the Eastern United
States, which has been studied especially at Ithaca,

N.Y. (Johannsen, 1903).

The eggs are deposited in a compact yellowish layer
on the surface of rock, on the brinks of falls and
rapids where the water is flowing swiftly. They are 75 Larva of Simu _
elongate ellipsoidal in shape, about .4 by .18 mm. AfteH^'rmam
As myriads of females deposit in the same place the
egg patches may be conspicuous coatings of a foot or much more
in diameter. When first laid they are enveloped in a yellowish

74. Mouth parts of Simulium. After
Grunberg.

Simuliidce, or Black Flies

105

white slime, which becomes darker, until finally it becomes black just
before the emerging of the larvae. The egg stage lasts a week.

The larvae (fig. 75) arc black, soft skinned, somewhat cylindrical
in shape, enlarged at both ends and attenuated in the middle. The
posterior half is much stouter than the anterior part and almost club-
shaped. The head bears two large fan-shaped organs which aid in
procuring food. Respiration is accomplished by means of three so-
called blood gills which are pushed out from the dorsal part of the
rectum. The larvae occur in enormous numbers, in moss-like patches.
If removed from their natural habitat and placed in quiet water they
die within three or four hours. Fastened to the rock by means of a
disk-like sucker at the caudal end of
the body, they ordinarily assume an
erect position. They move about on
the surface of the rocks, to a limited
extent, with a looping gait similar to
that of a measuring worm, and a web
is secreted which prevents their being
washed away by the swiftly flowing
water. They feed chiefly upon algas
and diatoms.

The complete larval stage during
the summer months occupies about
four weeks, varying somewhat with the
temperature and velocity of the water.

At the end of this period they spin 76 - simuiium venustum, (x8).

L j 1 After Garman.

from cephalic glands, boot-shaped

silken cocoons within which the} 7 pupate. The cocoon when spun
is firmly attached to the rock and also to adjacent cocoons.
Clustered continuously over a large area and sometimes one above
another, they form a compact, carpet-like covering on the rocks,
the reddish-brown color of which is easily distinguishable from the
jet-black appearance of the larvae. The pupal stage lasts about
three weeks. The adult fly, surrounded by a bubble of air, quickly
rises to the surface'of the water and escapes. The adults (fig. 76)
are apparently short lived and thus the entire life cycle, from egg
to egg is completed in approximately eight weeks.

In the case of Simuiium pictipes at Ithaca, N. Y., the first brood
of adults emerges early in May and successive generations are produced
throughout the summer and early autumn. This species winters in

io6

Parasitic Arthropoda

the larval condition. Most of the other species of Simulium which
have been studied seem to be single brooded.

While Simulium pictipes does not attack man, there are a number
of the species which are blood-sucking and in some regions they are a
veritable scourge. In recent years the greatest interest in the group
has been aroused by Sambon’s hypothesis that they transmit pellagra
from man to man. This has not been established, and, indeed, seems
very doubtful, but the importance of these insects as pests and the
possibility that they may carry disease make it urgent that detailed
life-histories of the hominoxious species be worked out.

As pests a vivid account of their attacks is in Agassiz’s “Lake
Superior’’ (p. 61), quoted by Forbes (1912).

“Neither the love of the picturesque, however, nor the interests of
science, could tempt us into the woods, so terrible were the black flies.
This pest of flies which all the way hither had confined our ramblings
on shore pretty closely to the rocks and the beach, and had been
growing constantly worse, here reached its climax. Although de¬
tained nearly two days, * * * we could only sit with folded

hands, or employ ourselves in arranging specimens, and such other
operations as could be pursued in camp, and under the protection of
a ‘smudge.’ One, whom scientific ardor tempted a little way up the
river in a canoe, after water plants, came back a frightful spectacle,
with blood-red rings round his eyes, his face bloody, and covered with
punctures. The next morning his head and neck were swollen as if
from an attack of erysipelas.”

There are even well authenticated accounts on record of death of
humans from the attacks of large swarms of these gnats. In some
regions, and especially in the Mississippi Valley in this country, cer¬
tain species of black flies have been the cause of enormous losses to
farmers and stockmen, through their attacks on poultry and domestic
animals. C. V. Riley states that in 1874 the loss occasioned in one
county in Tennessee was estimated at $500,000.

The measures of prevention and protection against these insects
have been well summarized by Forbes (1912). They arc of two kinds:
“the use of repellents intended to drive away the winged flies, and
measures for the local destruction of the aquatic larvae. The repel¬
lents used arc either smudges, or surface applications made to keep
the flies from biting. The black-fly will not endure a dense smoke,
and the well-known mosquito smudge seems to be ordinarily sufficient
for the protection of man. In the South, leather, cloth, and other

Simuliidce, or Black Flies

107

materials which will make the densest and most stifling smoke, are
often preserved for this use in the spring. Smudges are built in
pastures for the protection of stock, and are kept burning before the
doors of bams and stables. As the black-flies do not readily enter a
dark room, light is excluded from stables as much as possible during
the gnat season. If teams must be used in the open field while gnats
are abroad, they may be protected against the attacks of the gnats by
applying cotton-seed oil or axle grease to the surface, especially to the
less hairy parts of the animals, at least twice a day. A mixture of oil
and tar and, indeed, several other preventives, are of practical use in
badly infested regions; but no definite test or exact comparison has
been made with any of them in a way to give a record of the precise
results.”

‘‘It is easy to drive the flies from houses or tents by burning
pyrethrum powder inside; this either kills the flies or stupifies them
so that they do not bite for some time thereafter.” * * * ‘‘Oil of

tar is commonly applied to the exposed parts of the body for the pur¬
pose of repelling the insects, and this preparation is supplied by the
Hudson Bay Company to its employees. Minnesota fishermen
frequently grease their faces and hands with a mixture of kerosene
and mutton tallow for the same purpose.” We have found a mixture
of equal parts of kerosene and oil of pennyroyal efficient.

Under most circumstances very little can be done to destroy this
insect in its early stage, but occasionally conditions are such that a
larvicide can be used effectively. Weed (1904), and Sanderson (1910)
both report excellent results from the use of phinotas oil, a proprietary
compound. The first-mentioned also found that in some places the
larvae could be removed by sweeping them loose in masses with stiff
stable brooms and then catching them downstream on wire netting
stretched in the water.

Chironomidse or Midges

The flies of this family, commonly known as midges, resemble
mosquitoes in form and size but are usually more delicate, and the
wing-veins, though sometimes hairy, are not fringed with scales.
The venation is simpler than in the mosquitoes and the veins are
usually less distinct.

These midges, especially in spring or autumn, are often seen in
immense swarms arising like smoke over swamps and producing a
humming noise which can be heard for a considerable distance. At

io8

Parasitic Arthropoda

these seasons they are frequently to be found upon the windows of
dwellings, where they are often mistaken for mosquitoes.

The larvae are worm-like, but vary somewhat in form in the differ¬
ent genera. Most of them are aquatic, but a few live in the earth, in
manure, decaying wood, under bark, or in the sap of trees, especially
in the sap which collects in wounds.

Of the many species of Chironomidae, (over eight hundred known),
the vast majority are inoffensive. The sub-family Ceratopogoninae,
however, forms an exception, for some of the members of this group,

77 . Culicoides guttipennis; (a) adult, (x 15); (6) head of same; (e) larva;

C d ) head; (e) pupa. After Pratt.

known as sandflies, or punkies, suck blood and are particularly trouble¬
some in the mountains, along streams, and at the seashore. Most of
these have been classed under the genus Ceratopogon, but the group
has been broken up into a number of genera and Ceratopogon, in the
strict sense, is not known to contain any species which sucks the blood
of vertebrates.

[* The Ceratopogoninae — The Ceratopogoninae are among the smallest
of the Diptera, many of them being hardly a millimeter long and some
not even so large. They are Chironomidae in which the thorax is not
prolonged over the head. The antennae are filiform with fourteen
(rarely thirteen) segments in both sexes, those of the male being brush¬
like. The basal segment is enlarged, the last segment never longer

Chironomidce, or Midges

109

than the two preceding combined, while the last five are sub-equal to,
or longer than the preceding segment. The legs are relatively stouter
than in the other Chironomidae. The following three genera of this
subfamily are best known as blood suckers in this country.

Of the genus Culicoides there are many species occurring in various
parts of the world. A number are known to bite man and animals and
it is probable that all are capable of inflicting injury. In some
localities they are called punkies, in others, sand-flies, a name some¬
times also applied to the species of Simulium and Phlebotomus.
Owing to their very small size they are known by some tribes of
Indians as No-see-ums. The larva? are found in ponds, pools, water
standing in hollow tree stumps, and the like. Though probably living
chiefly in fresh water, we have found a species occurring in salt water.
The larvae are small, slender, legless,
worm-like creatures (fig. 77 c) with
small brown head and twelve body
segments. The pupae (fig. 77c) are
slender, more swollen at the anterior
end and terminating in a forked pro¬
cess. They float nearly motionless in
a vertical position, the respiratory
tubes in contact with the surface film.

The adults are all small, rarely exceed¬
ing 2>4 mm. in length. The wings
are more or less covered with erect
setulas or hairs and in many species
variously spotted and marked with
iridescent blotches. The antennae have fourteen segments, the palpi
usually five. The wing venation and mouth-parts are shown in
figures 77 and 78. Of the twenty or more species of this genus
occurring in the United States the following are known to bite: C.
cinctus, C. guttipennis, C. sanguisuga, C. stellifer, C. variipennis,
C. unicolor.

One of the most widely distributed and commonest species in the
Eastern States is C. guttipennis (fig. 77a). It is black with brown
legs, a whitish ring before the apex of each femur and both ends of
each tibia; tarsi yellow, knobs of halteres yellow. Mesonotum
opaque, brown, two vittae in the middle, enlarging into a large spot
on the posterior half, also a curved row of three spots in front of each
wing, and the narrow lateral margins, light gray pruinose. Wings

78. Culicoides guttipennis; mouth
parts of adult. After Pratt.

I IO

Parasitic Arthropoda

nearly wholly covered with brown hairs, gray, with markings as
shown in the figure. Length one mm.

Johannseniella Will, is a
wide-spread genus related
to the foregoing. Its
mouth-parts are well
adapted for piercing and
it is said to be a persistent
blood sucker, particularly
in Greenland. This genus
is distinguished from Culi-
coides by its bare wings,
the venation (fig. 163,0),
and the longer tarsal claws.
There are over twenty
North American species.

In the Southwestern United States, Tersesthes torrens Towns,
occurs, a little gnat which annoys horses, and perhaps man also, by
its bite. It is related to Culicoides but differs in the number of
antennal segments and in its wing venation (fig. i63,e). The fly
measures but two mm. in length and is blackish in color. The
antennae of the female have thirteen segments, the palpi but three, of
which the second is enlarged and swollen.

Tabanidae or Horse-Flies

The Tabanidae, horse-flies, ear-flies, and deer-flies, — are well-
known pests of cattle and horses and are often extremely annoying
to man. The characteristics of the family and of the principal North
American genera are given in the keys of Chapter XII. There are
•over 2500 recorded species. As in the mosquitoes, the females
alone are blood suckers. The males are flower feeders or live on
plant juices. This is apparently true also of the females of some of
the genera.

The eggs are deposited in masses on water plants or grasses and
sedges growing in marshy or wet ground. Those of a common
species of Tabanus are illustrated in figure 80, a. They are placed
in masses of several hundred, light colored when first deposited but
turning black. In a week or so the cylindrical larvae, tapering at
both ends (fig. 80, b ), escape to the water, or damp earth, and lead

Tabanidce, or Horse-flies

an active, carnivorous life, feeding mainly on insect larvae, and worms.
In the forms which have been best studied the larval life is a long

one, lasting for months or even for more
than a year. Until recently, little was
known concerning the life-histories of this
group, but the studies of Hart (1895),
and Hine (1903
+ ) have added
greatly to the
knowledge con¬
cerning North
American
forms.

Many of the
species attack
man with avid¬
ity and are able
to inflict painful
bites, which
may smart for
hours. In some
instances the
wound is so
considerable
that blood will
continue to flow
after the fly has
left. We have
seen several

cases of secondary infection following
such bites.

The horse-flies have been definitely
convicted of transferring the trypanosome
of surra from diseased to healthy animals
and there is good evidence that they transfer anthrax. The possi¬
bility of their being important agents in the conveyal of human
diseases should not be overlooked. Indeed, Leiper has recently
determined that a species of Chrysops transfers the blood parasite
Filaria diurna.

80. (6) Larva of Tabanus.

Photograph by M. V. S.

80. (a) Eggs of Tabanus. Photo¬

graph by J. T. Lloyd.

11 2

Leptidce, or Snipe-flies

Leptidae or Snipe-Flies

The family Leptidae is made up of moderate or large sized flies,
predaceous in habit. They are sufficiently characterized in the keys

of Chapter XII. Four blood¬
sucking species belonging to three
genera have been reported. Of
these Symphoromyia pachyceras is
a western species. Dr. J. C.
Bradley, from personal experience,
reports it as a vicious biter.

Oestridae or Bot-flies

To the family Oestridae belong
the bot and warble-flies so fre¬
quently injurious to animals.
The adults are large, or of
medium size, heavy bodied, rather
hairy, and usually resemble bees in appearance.

The larvae live parasitieally in various parts of the body of mam¬
mals, such as the stomach (horse bot-fly), the subcutaneous con¬
nective tissue (warble-fly of cattle), or the nasal passage (sheep bot¬
fly or head maggot).

There are on record many cases of the occurrence of the larvae
of Oestridae as occasional parasites of man. A number of these have
been collected and reviewed in a thesis by Mme. Petrovskaia (1910).
The majority of them relate to the following species.

Gasirophilus hcemorrhoidalis , the red tailed bot-fly, is one of the
species whose larvae are most commonly found in the stomach of the
horse. Schoch (1877) cites the case of a woman who suffered from
a severe case of chronic catarrh of the stomach, and who vomited,
and also passed from the anus, larvae which apparently belonged
to this species. vSuch cases are exceedingly rare but instances of
subcutaneous infestation are fairly numerous. In the latter type
these larvae are sometimes the cause of the peculiar “ creeping myasis.
This is characterized at its beginning by a very painful swelling
which gradually migrates, producing a narrow raised line four to
twenty-five millimeters broad. When the larva is mature, sometimes
after several months, it becomes stationary and a tumor is formed
which opens and discharges the larva along with pus and scrum.

80. ( c ) Mouth parts of Tabanus. After Gnin-

berg.

Oestridce, or Bot-flies

113

Gastrophilus equi is the most widespread and common of the horse
bot-flies. Portschinsky reports it as commonly causing subcutan¬
eous myasis of man in Russia.

Hypoderma bovis ( = Oestrus bovis), and Hypoderma lineata are
the so-called warble-flies of cattle. The latter species is the more
common in North America but Dr. C. G. Hewitt has recently shown
that H. bovis also occurs. Though warbles are very common in
cattle in this country, the adult flies are very rarely seen. They
are about half an inch in length, very hairy, dark, and closely resemble
common honey-bees.

They deposit their eggs on the hairs of cattle and the animals in
licking themselves take in the young larvae. These pass out through
the walls of the oesophagus and migrate through the tissues of the
animal, to finally settle down in the subcutaneous tissue of the back.
The possibility of their entering directly through the skin, especially
in case of infestation of man, is not absolutely precluded, although
it is doubtful.

For both species of Hypoderma there are numerous cases on
record of their occurrence in man. Hamilton (1893) saw a boy,
six years of age, who had been suffering for some months from the
glands on one side of his neck being swollen and from a fetid ulcera¬
tion around the back teeth of the lower jaw of the same side. Three
months’ treatment was of no avail and the end seemed near; one day
a white object, which was seen to move, was observed in the ulcer
at the root of the tongue, and on being extracted was recognized as a
full grown larva of Hypoderma. It was of usual tawny color, about
half an inch long when contracted, about one third that thickness,
and quite lively. The case resulted fatally. The boy had been on a
dairy farm the previous fall, where probably the egg (or larva) was
in some way taken into his mouth, and the larva found between the
base of the tongue and the jaw suitable tissue in which to develop.

Topsent (1901) reports a case of “creeping myasis” caused by
H. lineata in the skin of the neck and shoulders of a girl eight years
of age. The larva travelled a distance of nearly six and a half inches.
The little patient suffered excruciating pain in the place occupied by
the larva.

Hypoderma diana infests deer, and has been known to occur in
man.

Oestris ovis, the sheep bot-fly, or head maggot, is widely distrib¬
uted in all parts of the world. In mid-summer the flies deposit

Parasitic Arthropoda

114

living maggots in the nostrils of sheep. These larvse promptly pass
up the nasal passages into the frontal and maxi liars 7 sinuses, where
they feed on the mucous to be found there. In their migrations
they cause great irritation to their host, and when present in numbers
may cause vertigo, paroxysms, and even death. Portschinsky in an
important monograph on this species, has discussed in detail its
relation to man. He shows that it is not uncommon for the fly to
attack man and that the minute living larvse are deposited in the
eyes, nostrils, lips, or mouth. A typical case in which the larvae
w T ere deposited in the eye was described by a German oculist Kayser,
in 1905. A woman brought her six year old daughter to him and
said that the day before, about noontime, a flying insect struck the
eye of the child and that since then she had felt a pain which in¬
creased towards evening. In the morning the pain ceased but the
eye was very red. She was examined at about noon, at which time
she was quiet and felt no pain. She was not sensitive to light, and
the only thing noticed was a slight congestion and accumulation of
secretion in the comer of the right eye. A careful examination of
the eye disclosed small, active, white larvae that crawled out from
the folds of the conjunctiva and then back and disappeared. Five
of these larvae were removed and although an uncomfortable feeling
persisted for a while, the eye became normal in about three weeks.

Some of the other recorded cases have not resulted so favorably,
for the eyesight has been seriously affected or even lost.

According to Edmund and Etienne Sergent (1907), myasis caused
by the larvae of Oestris ovis is very common among the shepherds in
Algeria. The natives say that the fly deposits its larvae quickly,
while on the wing, without pause. The greatest pain is caused when
these larvae establish themselves in the nasal cavities. They then
produce severe frontal headaches, making sleep impossible. This
is accompanied by continuous secretion from the nasal cavities
and itching pains in the sinuses. If the larvae happen to get into
the mouth, the throat becomes inflamed, swallowing is painful,
and sometimes vomiting results. The diseased condition may last
for from three to ten days or in the case of nasal infection, longer,
but recovery' always follows. The natives remove the larvae from
the eye mechanically by means of a small rag. When the nose is
infested, tobacco fumigations are applied, and in case of throat
infestation gargles of pepper, onion, or garlic extracts are used.

Oestrides, or Bot-flies

Rhincestrus nasalis, the Russian gad-fly, parasitizes the naso¬
pharyngeal region of the horse. According to Portschinsky, it not

infrequently attacks man
and then, in all the known
cases deposits its larvae
in the eye, only. This
is generally done while
the person is quiet, but
not during sleep. The
fly strikes without stop¬
ping and deposits its larva
instantaneously. Imme¬
diately after, the victim
experiences lancinating
pains which without in¬
termission increase in
violence. There is an in¬
tense conjunctivitis and

81.

Larvae of Dermatobia cyaniventris.

chard.

After Blan-

if the larvae are not removed promptly the envelopes
ot the eye are gradually destroyed and the organ
lost.

Dermatobia cyaniventris —This fly (fig. 83) is widely
■distributed throughout tropical America, and in its
larval stage is well known as a parasite of man. The
larvae (figs. 81 and 82) which are known as the “ver
macaque,” “torcel,” “ver moyocuil” or by several other
local names, enter the skin and give rise to a boil-like
swelling, open at the top, and comparable with the swell¬
ing produced by the warble fly larvae, in cattle. They
cause itching and occasional excruciating pain. When
mature, nearly an inch in length, they voluntarily
leave their host, drop to the ground and complete their
development. The adult female is about 12 mm. in
length. The face is yellow, the frons black with a
grayish bloom; antennae yellow, the third segment
four times as long as the second, the arista pectinate.
The thorax is bluish black with grayish bloom; the
abdomen depressed, brilliant metallescent blue with
violet tinge. The legs are yellowish, the squamae and
wings brownish.

82. Young larva of
Dermatobia cy¬
aniventris.

After Surcouf.

n6 Parasitic Arthropoda

The different types of larvae represented in figure Si were formerly
supposed to belong to different species but Blanchard regards them

as merely various stages
of the same species. It
is only very recently
that the early stage and
the method by which
man becomes infested
were made known.

About 1900, Blanch¬
ard observed the pres¬
ence of packets of large¬
sized eggs under the
abdomen of certain mos-

83. Dermatobia cyaniventris (xlj<). After Graham-Smith. qUltoeS from Central

America; and in 1910,
Dr. Morales, of Costa Rica, declared that the Dermatobia deposited
its eggs directly under the abdomen of the mosquito and that they
were thus carried to vertebrates.

Dr. Nunez Tovar observed the
mosquito carriers of the eggs and
placing larvae from this source on
animals, produced typical tumors
and reared the adult flies. It
remained for Sureouf (1913) to
work out the full details. He
found that the Dermatobia de¬
posits its eggs in packets covered
by a very viscid substance, on
leaves. These become attached
to mosquitoes of the species
Janthinosoma lutzi (fig. 84) which
walk over the leaves. The eggs
which adhere to the abdomen,
remain attached and are thus
transported. The embryo de¬
velops, but the young larva (fig. 82) remains in the egg until it has
opportunity to drop upon a vertebrate fed upon by the mosquito.

84. Mosquito carrying eggs of Dermatobia
cyaniventris. After Sureouf.

The Muscidce

117

Muscidae

The following Muscidae, characterized elsewhere, deserve special
mention under our present grouping of parasitic species. Other
important species will be considered as facultative para¬
sites.

Stomoxys calcitrans, the stable-fly, or the biting house¬
fly, is often confused with Musca domestica and therefore
is discussed especially in our consideration of the latter
species as an accidental carrier of disease. Its possible
relation to the spread of infantile paralysis is also con¬
sidered later.

The tsetse flies, belonging to the genus Glossina, are
African species of blood-sucking Muscidae which have
attracted much attention because of their role in trans-
8.5 L arva of mitting various trypanosome diseases of man and animals.
oil' 13 ' After They are characterized in Chapter XII and are also
Smith am ’ di scusse d in connection with the diseases which they
convey.

Chrysomyia macellaria, (= Compsomyia ), the “screw worm”-fly
is one of the most important species of flies directly affecting man,
in North America. It is not normally parasitic, however, and hence
will be considered witlC other facultative parasites in Chapter IV.

Auchmeromyia lute-
ola, the Congo floor
maggot. This is a
muscid of grewsome
habits, which has a wide
distribution throughout
Africa. The fly (fig. 86)
deposits its eggs on the
ground of the huts of the
natives. The whitish
larvae (fig. 85) on hatch¬
ing are slightly flat¬
tened ventrally, and
each segment bears
posteriorly three foot¬
pads transversely arranged. At night the larvae find their way into the
low beds or couches of the natives and suck their blood. The adult
flies do not bite man and, as far as known, the larvae do not play any
role in the transmission of sleeping sickness or other diseases.

86. Auchmeromyia luteola (X4). After Graham-Smith.

118

Parasitic Arthropoda

87. Cordylobia anthropophaga (x3).
After Fulleborn.

This habit of blood-sucking by museid larvae is usually referred
to as peculiar to Aucheromyia luteola but it should be noted that the

larvae of Protocalliphora frequent the
nests of birds and feed upon the
young. Mr. A. F. Coutant has studied
especially the life-history and habits
of P. azurea, whose larvae he found
attacking young crows at Ithaca, N.Y.
He was unable to induce the larvae to
feed on man.

Cordylobia anthropophaga, ( Ochro -
myia anthropophaga), or Tumbu-fly
(fig. 87) is an African species whose
larva; affect man much as do those of
Dermatobia cyniventris, of Central and
South America. The larva (fig. 88), which is known as “ver du
Cayor” because it was first observed in Cayor, in Senegambia,
develops in the skin of man and of various animals, such as dogs,
cats, and monkeys. It is about 12 mm. in length, and of the form
of the larvae of other muscids. Upon the intermediate segments are
minute, brownish recurved spines which give to the larva its char¬
acteristic appearance. The life-history is not satisfactorily worked
out, but Fuller (1914), after reviewing
the evidence believes that, as a rule, it
deposits its young in the sleeping places
of man and animals, whether such be a
bed, a board, the floor, or the bare ground.

In the case of babies, the maggots may
be deposited on the scalp. The minute
maggots bore their way painlessly into
the skin. As many as forty parasites
have been found in one individual and
one author has reported finding more
than three hundred in a spaniel puppy.

Though their attacks are at times ex¬
tremely painful, it is seldom that any
serious results follow.

The Siphonaptera or Fleas 119

The Siphonaptera or Fleas

The Siphonaptera, or fleas (fig. 89) are wingless insects, with
highly chitinized and laterally compressed bodies. The mouth-parts
are formed for piercing and sucking. Compound eyes are lacking
but some species possess ocelli. The metamorphosis is complete.

This group of parasites, concerning which little was known until
recently, has assumed a very great importance since it was learned

that fleas are the carriers of bubonic plague. Now over four hundred
species are known. Of these, several species commonly attack man.
The most common hominoxious species are Pulex irritans, Xenopsylla
cheopis, Ctenocephalus cams, Ctenocephalus jelis, Ceratophyllus
fasciatus and Dermatophilus penetrans, but many others will feed
readily on human blood if occasion arises.

We shall treat in this place of the general biology and habits of
the hominoxious forms and reserve for the systematic section the
discussion of the characteristics of the different genera.

120

Parasitic Arthropoda

Dog flea (xl5). After Howard.

The most common fleas infesting houses in the Eastern United
States are the cosmopolitan dog and cat fleas, Ctenocephalus canis

(fig. 90) and C. felis. Their life
cycles will serve as typical.
These two species have until
recently been considered as one,
under the name Pulex serraticeps.
See figure 92.

The eggs are oval, slightly
translucent or pearly white, and
measure about .5 mm. in their
long diameter. They are de¬
posited loosely in the hairs of
the host and readily drop off as the animal moves around. Howard
found that these eggs hatch in one to two days. The larvae are
elongate, legless, white, worm-like creatures. They are .exceed¬
ingly active, and avoid the light in every way possible. They
east their first skin in from three to seven days and their second
in from three to four days. They commenced spinning in from
seven to fourteen days after hatching and the imago appeared
five days later. Thus in summer, at Washington, the entire life
cycle may be completed in about two weeks, (cf. fig. 91, 92).

Strickland’s (1914) studies on the biology of the rat flea, Cerato-
phyllus fasciatus, have so important a general bearing that we shall
cite them in considerable detail.

He found, to begin with, that there is a marked inherent range
in the rate of development. Thus, of a batch of seventy-three eggs,
all laid in the same day and kept together under the same condi-

91. Larva of Xenopsylla cheopis. After Bacot and Ridewood.

tions, one hatched in ten days; four in eleven days; twenty-five in
twelve days; thirty-one in thirteen days; ten in fourteen days; one
in fifteen days; and one in sixteen days. Within these limits the
duration of the egg period seems to depend mainly on the degree
of humidity. The incubation period is never abnormally prolonged

Siplionaptera, or Fleas

121

as in the case of lice, (Warburton) and varying conditions of tempera¬
ture and humidity have practically no effect on the percentage of
eggs which ultimately hatch.

The same investigator found that the most favorable condition
for the larva is a low temperature, combined with a high degree of
humidity; and that the presence of rubbish in which the larva may
bury itself is essential to its successful development. When larvae
are placed in a bottle containing either wood-wool soiled by excre¬
ment, or with feathers or filter paper covered with dried blood they

92. Head and pronotum of (a) deg flea; (b) of cat flea; (e) of hen flea. After Rothschild.
( d ) Nycteridiphilus (Ishnopsyllus) hexactenus. After Oudemans.

will thrive readily and pupate. They seem to have no choice be¬
tween dried blood and powdered rat feces for food, and also feed
readily on flea excrement. They possess the curious habit of always
devouring their molted skins.

An important part of Strickland’s experiments dealt with the
question of duration of the pupal stage under the influence of tempera¬
ture and with the longevity and habits of the adult. In October,
he placed a batch of freshly formed cocoons in a small dish that was
kept near a white rat in a deep glass jar in the laboratory. Two
months later one small and feeble flea had emerged, but no more
until February, four months after the beginning of the experiment.
Eight cocoons were then dissected and seven more found to contain
the imago fully formed but in a resting state. The remainder of

122

Parasitic Arthropoda

the batch was then placed at 70° F. for one night, near a white
rat. The next day all the cocoons were empty and the fleas were
found on the white rat.

Thus, temperature greatly influences the duration of the pupal
period, which in Ceratophyllus fasciatus averages seventeen days.
Moreover, when metamorphosis is complete a low temperature will
cause the imago to remain within the cocoon.

Sexually mature and ovipositing fleas, he fed at intervals and kept
alive for two months, when the experiment was discontinued. In
the presence of rubbish in which they could bury themselves, unfed
rat fleas were kept alive for many months, whereas in the absence of
any such substratum they rarely lived a month. In the former case,
it was found that the length of life is influenced to some degree by the
temperature and humidity. In an experiment carried out at 70° F.
and 45 per cent humidity, the fleas did not live for more than four
months, while in an experiment at 6o° F. and 70 per cent humidity
they lived for at least seventeen months. There was no indication
that fleas kept under these conditions sucked moisture from surround¬
ing objects, and those kept in bell jars, with an extract of flea-rubbish
on filter paper, did not live any longer than those which were not so
supplied.

Curiously enough, although the rat is the normal host of Cerato¬
phyllus fasciatus, it was found that when given the choice these fleas
would feed upon man in preference to rats. However, none of the
fleas laid eggs unless they fed on rat blood.

The experiments of Strickland on copulation and oviposition in
the rat flea showed that fleas do not copulate until they are sexually
mature and that, at least in the case of Ceratophyllus fasciatus, the
reproductive organs are imperfectly developed for some time (more
than a week) after emerging from the pupa. When mature, copula¬
tion takes place soon after the fleas have fed on their true host—the
rat—but not if they have fed on a facultative host only, such as man.
Copulation is always followed by oviposition within a very short,
time.

The effect of the rat’s blood on the female with regard to egg-
laying, Strickland concludes, is stimulating rather than nutritive,
as fleas that were without food for many months were observed to
lay eggs immediately after one feed. Similarly, the male requires,
the stimulus of a meal of rat’s blood before it displays any copulatory
activity.

Siphonaptera , or Fleas

123

Mitzmain (1910) has described in detail the act of biting on man,
as observed in the squirrel flea, Ceratophyllus acutus. “The flea
when permitted to walk freely on the arm selects a suitable hairy
space where it ceases abruptly in its locomotion, takes a firm hold
with the tarsi, projects its proboscis, and prepares to puncture the
skin. A puncture is drilled by the pricking epipharynx, the saw¬
tooth mandibles supplementing the movement by lacerating the
cavity formed. The two organs of the rostrum work alternately,
the middle piece boring, while the two lateral elements execute a
sawing movement. The mandibles, owing to their basal attach¬
ments, are, as is expressed by the advisory committee on plague
investigations in India ( Journal of Hygiene , vol. 6, No. 4, p. 499),
‘capable of independent action, sliding up and down but maintaining
their relative positions and preserving the lumen of the aspiratory
channel.’ The labium doubles back, the V-shaped groove of this
organ guiding the mandibles on either side.’’

‘ ‘ The action of the proboscis is executed with a forward movement
of the head and a lateral and downward thrust of the entire body.
As the mouth-parts are sharply inserted, the abdomen rises simultane¬
ously. The hind and middle legs are elevated, resembling oars.
The forelegs are doubled under the thorax, the tibia and tarsi resting
firmly on the epidermis serve as a support for the body during the
feeding. The maxillary palpi are retracted beneath the head and
thorax. The labium continues to bend, at first acting as a sheath
for the sawing mandibles, and as these are more deeply inserted, it
bends beneath the head with the elasticity of a bow, forcing the
mandibles into the wound until the maxillas are embedded in the skin
of the victim. When the proboscis is fully inserted, the abdomen
ceases for a time its lateral swinging.”

“The acute pain of biting is first felt when the mandibles have
not quite penetrated and subsequently during each distinct move¬
ment of the abdomen. The swinging of the abdomen gradually
ceases as it becomes filled with blood. The sting of the biting
gradually becomes duller and less sensitive as feeding progresses.
The movements of the elevated abdomen grow noticeably feebler
as the downward thrusts of the springy bow-like labium becomes less
frequent.”

“As the feeding process advances one can discern through the
translucent walls of the abdomen a constant flow of blood, caudally
from the pharynx, accompanied by a peristaltic movement. The

124

Parasitic Arthropoda

end of the meal is signified in an abrupt manner. The flea shakes
its entire body, and gradually withdraws its proboscis by lowering
the abdomen and legs and violently twisting the head.”

‘‘When starved for several days the feeding of the rat fleas is
conducted in a rather vigorous manner. As soon as the proboscis
is buried to the full length the abdomen is raised and there ensues a
gradual lateral swaying motion, increasing the altitude of the raised
end of the abdomen until it assumes the perpendicular. The flea is
observed at this point to gain a better foothold by advancing the
fore tarsi, and then, gradually doubling back the abdomen, it turns
with extreme agility, nearly touching with its dorsal side the skin
of the hand upon which it is feeding. Meanwhile, the hungry para¬
site feeds ravenously.”

‘‘It is interesting to note the peculiar nervous action which the
rodent fleas exhibit immediately when the feeding process is com¬
pleted or when disturbed during the biting. Even while the rostrum
is inserted to the fullest the parasite shakes its head spasmodically;
in a twinkling the mouth is withdrawn and then the flea hops away.”

A habit of fleas which we shall see is of significance in considering
their agency in the spread of bubonic plague, is that of ejecting blood
from the anus as they feed.

Fleas are famous for their jumping powers, and in control measures
it is of importance to determine their ability along this line. It is
often stated that they can jump about four inches, or, according to
the Indian Plague Commission Xenopsylla cheopis cannot hop farther
than five inches. Mitzmain (1910) conducted some careful experi¬
ments in which he found that the human flea, Pulex irritans, was
able to jump as far as thirteen inches on a horizontal plane. The
mean average of five specimens permitted to jump at will was seven
and three-tenths inches. The same species was observed to jump
perpendicularly to a height of at least seven and three-fourths inches.
Other species were not able to equal this record.

The effect of the bite of fleas on man varies considerably accord¬
ing to the individual susceptibility. According to Patton and Cragg,
this was borne out in a curious manner by the experiments of Chick
and Martin. ‘‘In these, eight human hosts were tried; in seven,
little or no irritation was produced, while in one quite severe inflam¬
mation was set up around each bite.” Of two individuals, equally
accustomed to the insects, going into an infested room, one may be
literally tormented by them while the other will not notice them.

Siphonaptera, or Fleas

125

Indeed it is not altogether a question of susceptibility, for fleas seem
to have a special predilection for certain individuals. The typical
itching wheals produced by the bites are sometimes followed, especi¬
ally after scratching, by inflammatory papules.

The itching can be relieved by the use of lotions of carbolic acid
(2-3 per cent), camphor, menthol lotion, or carbolated vaseline.
If forced to sleep in an infested room, protection from attacks can
be in a large measure gained by sprinkling pyre thrum, bubach, or
California insect powder between the sheets. The use of camphor,
menthol, or oil of eucalyptus, or oil of pennyroyal is also said to afford
protection to a certain extent.

In the Eastern United States the occurrence of fleas as household
pests is usually due to infested cats and dogs which have the run of
the house. We have seen that the eggs are not attached to the host
but drop to the floor when they are laid. Verrill, cited by Osbom,
states that on one occasion he was able to collect fully a teaspoonful
of eggs from the dress of a lady in whose lap a half-grown kitten had
been held for a short time. Patton and Cragg record seeing the
inside of a hat in which a kitten had spent the night, so covered with
flea eggs that it looked “as if it had been sprinkled with sugar from
a sifter.” It is no wonder that houses in which pets live become
overrun with the fleas.

One of the first control measures, then, consists in keeping such
animals out of the house or in rigorously keeping them free from fleas.
The latter can best be accomplished by the use of strong tar soap
or Armour’s “Flesope,” which may be obtained from most druggists.
The use of a three per cent solution of creolin, approximately four
teaspoonfuls to a quart of warm water, has also been recommended.
While this is satisfactory in the case of dogs, it is liable to sicken cats,
who will lick their fur in an effort to dry themselves. Howard
recommends thoroughly rubbing into the fur a quantity of pyrethrum
powder. This partially stupifies the fleas which should be promptly
swept up and burned.

He also recommends providing a rug for the dog or cat to sleep
on and giving this rug a frequent shaking and brushing, afterwards
sweeping up and burning the dust thus removed.

Since the larvas of fleas are very susceptible to exposure, the use
of bare floors, with few rugs, instead of carpets or matting, is to be
recommended. Thorough sweeping, so as to allow no accumulation
of dust in cracks and crevices will prove efficient. If a house is once

126

Parasitic Arthropoda

infested it may be necessary to thoroughly scrub the floors with hot
soapsuds, or to spray them with gasoline. If the latter method is
adopted, care must be taken to avoid the possibility of fire.

To clear a house of fleas Skinner recommends the use of flake
naphthalene. In a badly infested house he took one room at a time,
scattering on the floor five pounds of flake naphthalene, and closed
it for twenty-four hours. It proved to be a perfect and effectual
remedy and very inexpensive, as the naphthalene could be swept up
and transferred to other rooms. Dr. Skinner adds, “so far as I am
concerned, the flea question is solved and if I have further trouble
I know the remedy. I intend to keep the dog and cat.”

The late Professor Slingerland very effectively used hydrocyanic
acid gas fumigation in exterminating fleas in houses. In one case,
where failure was reported, he found on investigation that the house
had become thoroughly reinfested from pet cats, which had been left
untreated. Fumigation with sulphur is likewise efficient.

The fact that adult fleas are usually to be found on the floor,
when not on their hosts, was ingeniously taken advantage of by
Professor S. H. Gage in ridding an animal room at Cornell University
of the pests. He swathed the legs of a janitor with sticky fly-paper
and had him walk back and forth in the room. Large numbers of
the fleas were collected in this manner.

In some parts of the southern United States hogs are commonly
infested and in turn infest sheds, bams and even houses. Mr. H. E.
Vick informs us that it is a common practice to turn sheep into barn-
lots and sheds in the spring of the year to collect in their wool, the
fleas which abound in these places after the hogs have been turned
out.

It is a common belief that adult fleas are attracted to fresh meat
and that advantage of this can be taken in trapping them. Various
workers, notably Mitzman (1910), have shown that there is no basis
for such a belief.

The true chiggers — The chigoes, or true chiggers, are the most
completely parasitic of any of the fleas. Of the dozen or more known
species, one commonly attacks man. • This is Dermatophilus penetrans,
more commonly known as Sarcopsylla penetrans or Pulex penetrans.

This species occurs in Mexico, the West Indies, Central and South
America. There are no authentic records of its occurrence in the
United States although,.as Baker has pointed out, there is no reason

The True Chiggers

127

why it should not become established in Florida and Texas. It is
usually believed that Brazil was its original home. Sometime about
the middle of the nineteenth century it was introduced into West
Africa and has spread across that continent.

The males and the immature females of Dermatophilus penetrans
(fig. 93) closely resemble those of other fleas. They are very active
little brown insects about 1-1.2 mm. in size, which live in the dust of
native huts and stables, and in dry, sandy soil. In such places they
often occur in enormous numbers and become a veritable plague.

They attack not only man but various animals. According to
Castellani and Chalmers, “Perhaps the most noted feature is the way

93. Dermatophilus penetrans. Much enlarged. After Karsten.

in which it attacks pigs. On the Gold Coast it appeared to be largely
kept in existence by these animals. It is very easily captured in
the free state by taking a little pig with a pale abdomen, and placing
it on its back on the ground on which infected pigs are living. After
watching a few moments, a black speck will appear on the pig’s
abdomen, and quickly another and another. These black specks are
jiggers which can easily be transferred to a test tube. On examina¬
tion they will be found to be males and females in about equal
numbers.”

Both the males and females suck blood. That which characterizes
this species as distinguished from other fleas attacking man is that
when the impregnated female attacks she burrows into the skin
and there swells until in a few days she has the size and appearance of
a small pea (fig. 94). Where they are abundant, hundreds of the

128

Parasitic Arthropoda

94. Dermatophilus penetrans, gravid female. After Moniez.

pests may attack a single individual (fig. 95). Here they lie with the
apex of the abdomen blocking the opening. According to Fulle-

born (1908) they do not
penetrate beneath the
epidermis. The eggs are
not laid in the flesh of
the victim, as is some¬
times stated, but are
expelled through this
opening. The female
then dies, withers and
falls away or is expelled
by ulceration. Accord¬
ing to Brumpt, she first
quits the skin and then,
falling to the ground,
deposits her eggs. The
subsequent develop¬
ment in so far as known,
is like that of other fleas.

The chigoe usually
enters between the toes,
the skin about the roots
of the nails, or the soles

95. Chiggers in the sole of foot of man. Manson’s
Tropical Diseases. Permission of Cassell and Co.

Siphonaptera, or Fleas

129

of the feet, although it may attack other parts of the body. Mense
records the occurrence in folds of the epidermis, as in the neighbor¬
hood of the anus. They give rise to irritation
and unless promptly and aseptically removed
there often occurs pus formation and the
development of a more or less serious abscess.
Gangrene and even tetanus may ensue.

Treatment consists in the careful removal
of the insect, an operation more easily accom¬
plished a day or two after its entrance, than
at first, when it is unswollen. The ulcerated
point should then be treated with weak car¬
bolic acid, or tincture of iodine, or dusted
thoroughly with an antiseptic powder.

Castellani and Chalmers recommend as
prophylactic measures, keeping the house clean and keeping pigs,
poultry, and cattle away therefrom. “High boots should be used,
and especial care should be taken not to go to a ground floor bath¬
room with bare feet. The feet, especially the toes, and under the
nails, should be carefully examined every morning to see if any black

97. Echidnophaga gallinacea infesting head of chicken. After Enderlein.

dots can be discovered, when the jigger should be at once removed,
and in this way suppuration will be prevented. It is advisable,

130

Parasitic Arthropoda

also, to sprinkle the floors with carbolic lotion, Jeyes’ fluid, or with
pyrethrum powder, or with a strong infusion of native tobacco, as
recommended by Law and Castellani.”

Echidnopliaga gallinacea (fig. 96) is a widely distributed Hectopsyl-
lid attacking poultry (fig. 97). It occurs in the Southern and South¬
western United States and has been occasionally reported as attack¬
ing man, especially children. It is less highly specialized than
Dermatophilus penetrans , and does not ordinarily cause serious
trouble in man.

CHAPTER IV

ACCIDENTAL OR FACULTATIVE PARASITES

In addition to the many species of Arthropods which are normally
parasitic on man and animals, there is a considerable number of those
which may be classed as accidental or facultative parasites.

Accidental or facultative parasites are species which are normally
free-living, but which are able to exist as parasites when accidentally
introduced into the body of man or other animal. A wide range of
forms is included under this grouping.

Acarina

A considerable number of mites have been reported as accidental
or even normal, endoparasites of man, but the authentic cases are
comparatively few.

In considering such reports it is well to keep in mind von Siebold’s
warning that in view of the universal distribution of mites one should
be on his guard. In vessels in which animal and other organic
fluids and moist substances gradually dry out, mites are very abund¬
antly found. If such vessels are used without very careful prelimi¬
nary cleaning, for the reception of evacuations of the sick, or for the
reception of parts removed from the body, such things may be readily
contaminated by mites, which have no other relation whatever to
them.

Nevertheless, there is no doubt but that certain mites, normally
free-living, have occurred as accidental parasites of man. Of these
the most commonly met with is Tyroglyphus siro, the cheese-mite.

Tyroglyphus siro is a small mite of a whitish color. The male
measures about 500^ long by 250^ wide, the female slightly larger.
They live in cheese of almost any kind, especially such as is a little
decayed. “The individuals gather together in winter in groups or
heaps in the hollows and chinks of the cheese and there remain
motionless. As soon as the temperature rises a little, they gnaw
away at the cheese and reduce it to a powder. The powder is com¬
posed of excrement having the appearance of little grayish microscopic
balls; eggs, old and new, cracked and empty; larvae, nymphs, and
perfect mites, cast skins and fragments of cheese, to which must be
added numerous spores of microscopic fungi.” — Murray.

132

Accidental or Facultative Parasites

Tyroglyphus siro, and related species, have been found many
times in human feces, under conditions which preclude the explana¬
tion that the contamination occurred outside of the body. They
have been supposed to be the cause of dysentery, or diarrhoea, and
it is probable that the Acarus dysenteries of Linnaeus, and Latreille,
was this species. However, there is little evidence that the mites
cause any noteworthy symptoms, even when taken into the body
in large numbers.

Histiogaster spermaticus (fig. 152) is a Tyroglyphid mite which
was reported by Trouessart (1902) as having been found in a cyst
in the groin, adherent to the testis. When the cyst was punctured,
it yielded about two ounces of opalescent fluid containing spermatozoa
and numerous mites in all stages of development. The evidence
indicated that a fecundated female mite had been introduced into
the urethra by means of an unclean catheter. Though Trouessart
reported the case as that of a Sarcoptid, Banks places the genus
Histiogaster with the Tyroglyphidae. He states that our species
feeds on the oyster-shell bark louse, possibly only after the latter is
dead, and that in England a species feeds within decaying reeds.

Nephrophages sanguinarius is a peculiarly-shaped, angular mite
which was found by Miyake and Scriba (1893) for eight successive
days in the urine of a Japanese suffering from fibrinuria. Males,
.117 mm. long by .079 mm. wide, females .36 mm. by .12 mm.,
and eggs were found both in the spontaneously emitted urine and in
that drawn by means of a catheter. All the mites found were dead.
The describers regarded this mite as a true endoparasite, but it is
more probable that it should be classed as an accidental parasite.

Myriapoda

There are on record a number of cases of myriapods occurring as
accidental parasites of man. The subject has been treated in detail
by Blanchard (1898 and 1902), who diserrssed forty cases. Since
then at least eight additions have been made to the list.

Neveau-Lamaire (1908) lists thirteen species implicated, repre¬
senting eight different genera. Of the Chilognatka there are three,
Julus terrestris, J. londinensis and Polydesmus complanatus. The
remainder are Chilopoda, namely, Lithobius forficatus, L. malenops,
Geophilus carpophagus , G. electricus, G. similis, G. cephalicus, Scutigera
coleoptrata, Himantarium gervaisi, Cluetechelyne vesuviana and
Stigniatogaster subterraneus.

Myriapoda

133

The majority of the cases relate to infestation of the nasal fossae,
or the frontal sinus, but intestinal infestation also occurs and there
is one recorded case of the presence of a species in Julus (fig. 13) in
the auditory canal of a child.

In the nose, the myriapods have been known to live for months
and according to some records, even for years. The symptoms
caused by their presence are inflammation, with or without increased
flow of mucus, itching, more or less intense headache, and at times
general symptoms such as vertigo, delirium, convulsions, and the
like. These symptoms disappear suddenly when the parasites are
expelled.

In the intestine of man, myriapods give rise to obscure symptoms
suggestive of infestation by parasitic worms. In a case reported by
Verdun and Bruyant (1912), a child twenty months of age had been
affected for fifteen days by digestive disturbances characterized by
loss of appetite, nausea and vomiting. The latter had been partic¬
ularly pronounced for three days, when there was discovered in the
midst of the material expelled a living myriapod of the species
Chcetechelyne vesuviana. Anthelminthics had been administered
without result. In some of the other cases, the administration of
such drugs had resulted in the expulsion of the parasite through the
anus.

One of the extreme cases on record is that reported by Shipley
(1914). Specimens of Geoplulus gorizensis (= G. subterraneus)
‘were vomited and passed by a woman of 68 years of age. Some of
the centipedes emerged through the patient’s nose, and it must be
mentioned that she was also suffering from a round worm. One of
her doctors was of the opinion that the centipedes were certainly
breeding inside the lady’s intestines, and as many as seven or eight,
sometimes more, were daily leaving the alimentary canal.”

‘‘According to her attendant’s statements these centipedes had
left the body in some hundreds during a period of twelve or eighteen
months. Their presence produced vomiting and some hsematemesis,
and treatment w r ith thymol, male-fern and turpentine had no effect
in removing the creatures.”

The clinical details, as supplied by Dr. Theodore Thompson were
as follows:

‘‘Examined by me July, 1912, her tongue was dry and glazed.
There was bleeding taking place from the nose and I saw a living
centipede she had just extracted from her nostril. Her heart, lungs

i34

Accidental or Facultative Parasites

and abdomen appeared normal. She was not very wasted, and did
not think she had lost much flesh, nor was there any marked degree
of anemia.”

Shipley gives the following reasons for believing it impossible
that these centipedes could have multiplied in the patient’s intestine.
‘‘The breeding habits of the genus Geophilus are peculiar, and ill
adapted for reproducing in such a habitat. The male builds a small
web or nest, in which he places his sperm, and the female fertilizes
herself from this nest or web, and when the eggs are fertilized they
are again laid in a nest or web in which they incubate and in two or
three weeks hatch out. The young Geophilus differ but very little
from the adult, except in size. It is just possible, but improbable,
that a clutch of eggs had been swallowed by the host when eating
some vegetables or fruit, but against this is the fact that the Geophilus
does not lay its eggs upon vegetables or fruit, but upon dry wood or
earth. The egg-shell is very tough and if the eggs had been swallowed
the egg-shells could certainly have been detected if the dejecta were
examined. The specimens of the centipede showed very little signs
of being digested, and it is almost impossible to reconcile the story
of the patient with what one knows of the habits of the centipedes.”

In none of the observed cases have there been any clear indica¬
tions as to the manner of infestation. It is possible that the myria¬
pods have been taken up in uncooked fruit or vegetables.

Lepidopterous Larvae

Scholeciasis — Hope (1837) brought together six records of infesta¬
tion of man by lepidopterous larvae and proposed to apply the name
scholeciasis to this type of parasitism. The clearest case was that
of a young boy who had repeatedly eaten raw cabbage and who
vomited larva; of the cabbage butterfly, Pieris brassiere. Such cases
are extremely rare, and there are few reliable data relative to the
subject. In this connection it may be noted that Spuler (1906) has
described a moth whose larvae live as ectoparasites of the sloth.

COLEOPTERA

Canthariasis —By this term Hope designated instances of acci¬
dental parasitism by the larvae or adults of beetles. Reports of
such cases are usually scouted by parasitologists but there seems no
good basis for wholly rejecting them. Cobbold refers to a half
dozen cases of accidental parasitism by the larvae of Flaps mortisaga.

Dipterous Larvae

i35

In one of these cases upwards of 1200 larvae and several perfect
insects were said to have been passed per anum. French (1905)

reports the case of a man
who for a considerable period
voided adult living beetles
of the species Nitidula
bipustulata. Most of the
other cases on record relate
to the larvae of Dermestidce
(larder beetles et al .) or
Infestation probably occurs
through eating raw or imperfectly cooked foods containing eggs or
minute larvae of these insects.

Brumpt cites a curious case of accidental parasitism by a coleopter¬
ous larva belonging to the genus Necrobia. This larva was extracted
from a small tumor, several millimeters long, on the surface of the
conjunctiva of the eye. The larvae of this genus ordinarily live in
decomposing flesh and cadavers.

Dipterous Larvae

Myasis— By this term (spelled also myiasis, and myiosis), is
meant parasitism by dipterous larvae. Such parasitism may be
normal, as in the cases already described under the heading parasitic
Diptera, or it may be facultative, due to free-living larvae being
accidentally introduced
into wounds or the body-
cavities of man. Of this
latter type, there is a
multitude of cases on
record, relating to com¬
paratively few species.

The literature of the sub¬
ject, like that relating
to facultative parasitism
in general, is unsatis¬
factory, for most ot the

determinations of species 99 . Piophila casei. After Graham-Smith.

have been very loose.

Indeed, so little has been known regarding the characteristics of
the larvae concerned that in many instances they could not be exactly

98. Larva of Piophila casei. Caudal aspect of larva.
Posterior stigmata.

Tenebrionidce (meal infesting species).

136

Accidental or Facultative Parasites

determined. Fortunately, several workers have undertaken com¬
parative studies along this line. The most comprehensive publica¬
tion is that of Banks (1912), entitled “The structure of certain dip¬
terous larvae, with particular reference to those in human food.”

Without attempting an exhaustive list, we shall discuss here the
more important species of Diptera whose larvae are known to cause
myasis, either external or internal. The following key will serve
to determine those most likely to be encountered. The writers
would be glad to examine specimens not readily identifiable, if
accompanied by exact data relative to occurrence.

a. Body more or less flattened, depressed; broadest in the middle, each segment

with dorsal, lateral, and ventral fleshy processes, of which the laterals,
at least, are more or less spiniferous (fig. 101). Fannia ( = Homalomyia).
In F. canicularis the dorsal processes are nearly as long as the laterals;
in F. scalaris the dorsal processes are short spinose tubercles.
aa. Body cylindrical, or slender conical tapering toward the head; without
fleshy lateral processes (fig. 105).

b. With the posterior stigmata at the end of shorter or longer tubercles, or if not

placed upon tubercles, then not in pit; usually without a “marginal button”
and without a chitinous ring surrounding the three slits; the slits narrowly
or broadly oval, not bent (fig. 171 i). Acalyptrate muscidce and some species
of Anthomyiidce. To this group belong the cheese skipper ( Piophila casei,
figs. 98, 99), the pomace-fly ( Drosophila ampelophila) , the apple maggot
(Rhagoletis pomonella) , the cherry fruit fly ( Rhagoletis cingulata ), the small
dung fly ( Sepsis violacea, fig. 170), the beet leaf-miner ( Pegomyia vicina,
fig. 171 i), the cabbage, bean and onion maggots ( Pliorbia spp.) et. al.
bb. Posterior stigmata of various forms, if the slits are narrowly oval (fig. 171)
then they are surrounded by a chitin ring which may be open ventro-
mesally.

c. Integument leathery and usually strongly spinulose; larvae hypodermatic or

endoparasitic.Bot flies (fig. 171, f, g, k). — Oestridce

cc. Integument not leathery and (except in Protocalliphora ) spinulse restricted
to transverse patches near the incisures of the segments.

d. The stigmal plates in a pit; the lip-like margin of the pit with a number of

fleshy tubercles; chitin of the stigma not complete; open ventro-mesally,

button absent (fig. 171 e).Flesh flies. — Sarcophaga

dd. Stigmata not in a pit.

e. The chitin ring open ventra-mesally; button absent (fig. 171 c). Screw-

worm fly . Chrysomyia

ee. The chitin ring closed.

/. vSlits of the posterior stigmata straight; marginal “button” present (fig. 171 b);
two distinct mouth hooks, fleshy tubercles around the anal area. Phormia
(fig. 171 f), Lucilia and Calliphora (fig. 172, a, b), Protocalliphora (fig. 171, j),
Cynomyia (fig. 171, a). Blow flies, bluebottle flies . Calliphorince

Dipterous Larva

i37

//. Slits of the posterior stigmata sinuous or bent. Subfamily Muscinae.
g. Slits of the posterior stigmata bent; usually two mouth hooks. Muscina
stabulans (fig. 171, /), Muscina similis, Myiospila meditatunda (fig. 172, i),
and some of the higher Anthomyiidce.

gg. Slits of the posterior stigmata sinuous; mouth hooks usually consolidated
into one. The house-fly ( Musca domestica fig. 171, d), the stable fly
(Stomoxys calcitrans) the horn fly ( Lyperosia irritans), Pyrellia, Psendo-
pyrellia, Morellia, Mesembrina. Polietes, et. al. (fig. 172 in part).

Eristalis — The larvse of Eristalis are the so-called rat-tailed mag¬
gots, which develop in foul water. In a few instances these larvae
have been known to pass through the human alimentary canal
uninjured. Hall and Muir (1913) report the case of a boy five years
of age, who had been ailing for ten weeks and who was under treat¬
ment for indigestion and chronic constipation. For some time he
had vomited everything he ate. On administration of a vermifuge
he voided one of the rat-tailed maggots of Eristalis. He admitted
having drunk water from a ditch full of all manner of rotting matter.
It was doubtless through this that he became infested. It is worth
noting that the above described symptoms may have been due to
other organisms or substances in the filthy water.

Piophila casei, the cheese-fly (fig. 99), deposits its eggs not only
in old cheeses, but on ham, bacon, and other fats. The larvae (fig. 98)
are the well-known cheese skippers, which sometimes occur in great
abundance on certain kinds of cheese. Indeed, some people have
a comfortable theory that such infested cheese is especially good.
Such being the case, it is small wonder that this species has been
repeatedly reported as causing intestinal myasis. Thebault (1901)
describes the case of a girl who, shortly after consuming a large piece
of badly infested cheese, became ill and experienced severe pains
in the region of the navel. Later these extended through the entire
alimentary canal, the excrement was mixed with blood and she
suffered from vertigo and severe headaches. During the four fol¬
lowing days the girl felt no change, although the excretion of the blood
gradually diminished and stopped. On the fourth day she voided
two half-digested larvae and, later, seven or eight, of which two were
alive and moving.

That these symptoms may be directly attributed to the larvae,
or “skippers,”has been abundantly shown by experimental evidence.
Portschinsky cites the case of a dog fed on cheese containing the
larvae. The animal suffered much pain and its excrement contained
blood. On post mortem it was found that the small intestine through-

133

Accidental or Facultative Parasites

out almost its entire length was marked by bloody bruises. The
papillse on these places were destroyed, although the walls were
not entirely perforated. In the appendix were found two or three
dead larvae. Alessandri (1910) has likewise shown that the larvae
cause intestinal lesions.

According to Graham-Smith, Austen (1912) has recorded a case
of myasis of the nose, attended with a profuse watery discharge of
several weeks duration and pain, due to the larvae of Piophila casei.

Anthyomyiidae—The characteristic larvae of two species of Fannia
( = Homalomyia or Anthomyia, in part) (fig. 101) are the most com¬

monly reported of dip¬
terous larvae causing intes¬
tinal myasis. Hewitt
(1912) has presented a
valuable study of the bio¬
nomics and of the larvae
of these flies, a type of
what is needed for all the
species concerned in my¬
asis. We have seen two
cases of their having been

100. Fannia canicularis (x4). After Graham-Smith.

passed in stools, without having caused any special symptoms.
In other instances their presence in the alimentary canal has given
rise to symptoms vaguely described as those of tapeworm infestation,
or helminthiasis. More specifically, they have been described as
causing vertigo, severe headache, nausea and vomiting, severe
abdominal pains, and in some instances, bloody diarrhoea.

One of the most striking cases is that reported by Blankmeyer
(1914), of a woman whose illness began fourteen years previously
with nausea and vomiting. After several months of illness she began
passing larvae and was compelled to resort to enemas. Three years
previous to the report, she noticed frequent shooting pains in the
rectal region and at times abdominal tenderness was marked. There
was much mucus in the stools and she “experienced the sensation
of larvae crawling in the intestine.” Occipital headaches were
marked, with remissions, and constipation became chronic. The
appetite was variable, there was a bad taste in the mouth, tongue
furred and ridged, and red at the edges. Her complexion was sal¬
low, and general nervousness was marked. As treatment, there
were given doses of magnesium sulphate before breakfast and at

A nthyomyiidce

i39

4 p. m. , with five grain doses of salol four times a day. The customary
parasiticides yielded no marked benefit. At the time of the report
the patient passed from four to fifty larvae per day, and was showing
some signs of improvement. The nausea had disappeared, her
nervousness was less evident, and there was a slight gain in weight.

The case was complicated by various other disorders, but the
symptoms given above seem to be in large part attributable to the
myasis. There is nothing in the case to justify the assumption
that larvae were continuously present, for years. It seems more
reasonable to suppose that something in the habits of the patient
favored repeated infestation. Nevertheless, a study of the various
cases of intestinal myasis caused by these and
other species of dipterous larvae seems to indi¬
cate that the normal life cycle may be con¬
siderably prolonged under the unusual conditions.

The best authenticated cases of myasis of the
urinary passage have been due to larvae of
Fannia. Chevril (1909) collected and described
twenty cases, of which seven seemed beyond
doubt. One of these was that of a woman of
fifty-five who suffered from albuminuria, and
urinated with much difficulty, and finally passed
thirty to forty larvae of Fannia canicularis.

It is probable that infestation usually occurs
through eating partially decayed fruit or vege¬
tables on which the flies have deposited their
eggs. Wellman points out that the flies may
deposit their eggs in or about the anus of
persons using outside privies and Hewitt
believes that this latter method of infection is probably the common
one in the case of infants belonging to careless mothers. “Such
infants are sometimes left about in an exposed and not very clean
condition, in consequence of which flies are readily attracted to them
and deposit their eggs.”

Muscinae—The larvae of the common house-fly, Mnsca domestica,
are occasionally recorded as having been passed with the feces or
vomit of man. While such cases may occur, it is probable that in
most instances similar appearing larvae of other insects have been
mistakenly identified.

101. Larva of Fannia
scalaris.

Accidental or Facultative Parasites

140

Muscina stabulans is re¬
garded by Portschinsky
(1913) as responsible for
many of the cases of intesti¬
nal mvasis attributed to other
species. He records the case
of a peasant who suffered from
pains in the lower part of the
breast and intestines, and
whose stools were mixed with
blood. F rom N ovember until
March he had felt particu¬
larly ill, being troubled with
nausea and vomiting in addi¬
tion to the pain in his intestines. In March, his physician prescribed
injections of a concentrated solution of tannin, which resulted in the
expulsion of fifty living larvae of Muscina stabulans. Thereafter
the patient felt much better, although he suffered from intestinal
catarrh in a less severe form.

Calliphorinae — Closely related to the Sarcophagidae are the
Calliphorince. to which group belong many of the so-called “blue
bottle” flies. Their larvae feed upon dead animals, and upon fresh
and cooked meat. Those of Pro-
tocalliphora, already mentioned,
are ectoparasitic on living nestling
birds. Larvae of Lucilia, we have
taken from tumors on living turtles.

To this sub-family belongs also
Auchqromyia luteola, the Congo
floor maggot. Some of these,
and at least the last mentioned,
are confirmed, rather than faculat-
tive parasites. Various species of
Calliphorinae are occassionally met
with as facultative parasites of

103. Lucilia caesar, (x 3 ). After Howard.

man.

Chrysomyia macellaria, the screw worm fly (fig. 107), is the fly
which is responsible for the most serious cases of human myasis in
the United States. It is widely distributed in the United States

102. Muscina stabulans (X4). After Graham
Smith.

Chrysomyia macellaria

141

but is especially abundant in the south. While the larvas b ] n
decaying matter in general, they so commonly breed in the living
flesh of animals that they merit rank as true parasites. The females
are attracted to open wounds of all kinds on cattle and other animals
and quickly deposit large numbers of eggs. Animals which have
been recently castrated, dehorned, or branded, injured by barbed
wire, or even by the attacks of ticks are promptly attacked in the
regions where the fly abounds. Even the navel of young calves or
discharges from the vulva of cows may attract the insect.

Not infrequently the fly attacks man, being attracted by an of¬
fensive breath, a chronic catarrh, or a purulent discharge from the
ears. Most common are the cases where the eggs are deposited in

104. Calliphora erythrocephala, (x6). After Graham-Smith.

the nostrils. The larvae, which are hatched in a day or two, are
provided with strong spines and proceed to bore into the tissues
of the nose, even down into or through the bone, into the frontal
sinus, the pharynx, larynx, and neighboring parts.

Osborn (1896) quotes a number of detailed accounts of the attacks
of the Chrysomyia on man. A vivid picture of the symptomology
of rhinal myasis caused by the larvae of this fly is given by Castellani
and Chalmers: “Some couple of days after a person suffering from
a chronic catarrh, foul breath, or ozacna, has slept in the open or has
been attacked by a fly when riding or driving, — i.e., when the hands
are engaged — signs of severe catarrh appear, accompanied with
inordinate sneezing and severe pain over the root of the nose or the
frontal bone. Quickly the nose becomes swollen, and later the face
also may swell, while examination of the nose may show the presence

142

Accidental or Facultative Parasites

of the larvae. Left untreated, the patient rapidly becomes worse,
and pus and blood are discharged from the nose, from which an
offensive odor issues. Cough appears as well as fever, and often
some delirium. If the patient lives long enough, the septum of the
nose may fall in, the soft and hard palates may be pierced, the wall
of the pharynx may be destroyed. By this time, however, the course
of the disease will have become quite evident by the larvae dropping
out of the nose, and if the patient continues to live all the larvae
may come away naturally.”

For treatment of rhinal myasis these writers recommend douch¬
ing the nose with chloroform water or a solution of chloroform in
sweet milk (10-20 per cent), followed by douches of mild antiseptics.
Surgical treatment may be necessary.

Sarcophagidae —The larvae (fig. 105) of flies of this family usually
feed upon meats, but have been found in cheese, oleomargerine,
pickled herring, dead and living insects, cow dung and human feces.
Certain species are parasitic in insects. Higgins (1890) reported
an instance of “hundreds” of larvae of Sarcophaga being vomited by a
child eighteen months of age. There was no doubt as to their origin
for they were voided while the physician was in the room. There
are many other reports of their occurrence in the alimentary canal.
We have recorded elsewhere (Riley, 1906) a case in which some ten
or twelve larvae of Sarcophaga were found feeding on the diseased
tissues of a malignant tumor. The tumor, a melanotic sarcoma,
was about the size of a small walnut, and located in the small of the
back of an elderly lady. Although they had irritated and caused a
slight hemorrhage, neither the patient nor others of the family knew

SarcophagidcB

143

of their presence. Any discomfort which they had caused had been
attributed to the sarcomatous growth. The infestation occurred

106. A flesh fly (Sarcophaga), (X 4 ). After Graham-Smith.

in mid-summer. It is probable that the adult was attracted by the
odor of the discharges and deposited the living maggots upon the
diseased tissues.

According to Kiichenmeister, Sarcophaga carnaria (fig. 106),
attracted by the odor, deposits its eggs and larvae in the vagina of
girls and women when they lie naked in hot summer days upon dirty
clothes, or when they have a discharge from the vagina. In malig¬
nant inflammations of the eyes the larvae
even nestle under the eyelids and in
Egypt, for example, produce a very
serious addition to the effects of small¬
pox upon the cornea, as according to
Pruner, in such cases perforation of the
cornea usually takes place.

Wohlfartia magnifica is another
Sarcophagid which commonly infests
man in the regions where it is abun¬
dant. It is found in all Europe but is
especially common in Russia, where
Portschinsky has devoted much atten¬
tion to its ravages. It deposits living
larvse in wounds, the nasal fossae, the
ears and the eyes, causing injuries
even more revolting than those described for Chrysomyia.

CHAPTER V

ARTHROPODS AS SIMPLE CARRIERS OF DISEASE

The fact that certain arthropods are poisonous, or may affect the
health of man as direct parasites has always received attention in
the medical literature. We come now to the more modern aspect
of our subject,—the consideration of insects and other arthropods
as transmitters and disseminators of disease.

The simplest way in which arthropods may function in this
capacity is as simple carriers of pathogenic organisms. It is con¬
ceivable that any insect which has access to, and comes in contact
with such organisms and then passes to the food, or drink, or to the
body of man, may in a wholly accidental and incidental manner
convey infection. That this occurs is abundantly proved by the
work of recent years. We shall consider as typical the case against
the house-fly, which has attracted so much attention, both popular
and scientific. The excellent general treatises of Hewitt (1910),
Howard (1911), and Graham-Smith (1913), and the flood of bulletins
and popular literature render it unnecessary to consider the topic
in any great detail.

The House-fly as a Carrier of Disease

Up to the past decade the house-fly has usually been regarded as a
mere pest. Repeatedly, however, it had been suggested that it
might disseminate disease. We have seen that as far back as the
sixteenth century, Mercurialis suggested that it was the agent in the
spread of bubonic plague, and in 1658, Kircher reiterated this view.
In 1871, Leidy expressed the opinion that flies were probably a means
of communicating contagious diseases to a greater degree than was
generally suspected. From what he had observed regarding gangrene
in hospitals, he thought flies should be carefully excluded from
wounds. In the same year, the editor of the London Lancet, referring
to the belief that they play a useful role in purifying the air said,
“Far from looking upon therh as dipterous angels dancing attendance
on Hygeia, regard them rather in the light of winged sponges spread¬
ing hither and thither to carry out the foul behests of Contagion.”

These suggestions attracted little attention from medical men, for
it is only within very recent years that the charges have been sup¬
ported by direct evidence. Before considering this evidence, it is

144

The House-fly as a Carrier of Disease

i45

necessary that we define what is meant by “house-fly” and that we
then consider the life-history of the insect.

There are many flies which are occasionally to be found in houses,
but according to various counts, from 95 per cent to 99 per cent of
these in warm weather in the Eastern United States belong to the
one species Musca domestica (fig. 108). This is the dominant house¬
fly the world over and is the one which merits the name. It has been
well characterized by Schiner (1864), whose description has been
freely translated by Hewitt, as follows:

“ Frons of male occupying a fourth part of the breadth of the head.
Frontal stripe of female narrow in front, so broad behind that it
entirely fills up the width of the frons. The dorsal region of the
thorax dusty grey in color with four equally broad longitudinal
stripes. Scutellum gray with black sides. The light regions of
the abdomen yellowish, transparent, the darkest parts at least at
the base of the ventral side yellow. The last segment and a dorsal
line blackish brown. Seen from behind and against the light, the
whole abdomen shimmering yellow, and only on each side of the
dorsal line on each segment a dull transverse band. The lower part
of the face silky yellow, shot with blackish brown. Median stripe
velvety black. Antennas brown. Palpi black. Legs blackish
brown. Wings tinged with pale gray with yellowish base. The
female has a broad velvety back, often reddishly shimmering frontal
stripe, which is not broader at the anterior end than at the bases of
the antennas, but become so very much broader above that the light
dustiness of the sides is entirely obliterated. The abdomen gradu¬
ally becoming darker. The shimmering areas on the separate seg¬
ments generally brownish. All the other parts are the same as in
the male.”

The other species of flies found in houses in the Eastern United
States which are frequently mistaken for the house or typhoid fly
may readily be distinguished by the characters of the following key:

a. Apical cell (R s ) of the wide wing open, i.e., the bounding veins
parallel or divergent (fig. 100). Their larvae are flattened, the
intermediate body segments each fringed with fleshy, more or
less spinose, processes. Fannia

b. Male with the sides of the second and third abdominal seg¬
ments translucent yellowish. The larva with three pairs
of nearly equal spiniferous appendages on each segment,

146 Arthropods as Simple Carriers of Disease

arranged in a longitudinal series and in addition two pairs
of series of smaller processes (fig. 100) F. canicidaris
bb. Male with blackish abdomen, middle tibia with a tubercle
beyond the middle. The larva with spiniferous appen¬
dages of which the dorsal and ventral series are short, the
lateral series long and feathered (fig. 101). . . .F.scalaris
aa. Apical cell (R) of the wing more or less narrowed in the
margin; i. e., the bounding veins more or less converging
(fig. 108).

b. The mouth-parts produced and pointed, fitted for piercing,

c. Palpi much shorter than the proboscis; a brownish gray
fly, its thorax with three rather broad whitish stripes;
on each border of the middle stripe and on the mesal
borders of the lateral stripes is a blackish brown line.
Abdomen yellowish brown; on the second, third and
fourth segments are three brown spots which may be
faint or even absent. The larvae live in dung. The

stable-fly (fig. no). Stomoxys calcitrans

cc. Palpi nearly as long as the proboscis. Smaller species
than the house-fly. The horn-fly (fig. 167)

Hcematohia irritans

bb. Mouth-parts blunt, fitted for lapping.

c. Thorax, particularly on the sides and near the base of the
wings with soft golden yellow hairs among the bristles.
This fly is often found in the house in very early spring
or even in the winter. The cluster-fly, Pollenia rudis
cc. Thorax without golden yellow hairs among the bristles,

d. The last segment of the vein M with an abrupt
angle, (fig. 108). The larvae live in manure,

etc.House-fly, Musca domestica

dd. The last segment of vein M with a broad, gentle
curve (fig. 102).

e. Eyes microscopically hairy; each abdominal
segment with two spots. Larvae in dung.

Myiospila meditahunda

ee. Eyes bare ; abdomen gray and brown marbled.

Muscina

f. With black legs and palpi. M. assimilis

The House-fly as a Carrier of Disease

147

ff. With legs more or less yellowish; palpi
yellow. Larvae in decaying vegetable
substances, dung, etc. M. stabulans

It is almost universally believed that the adults of Musca domestica
hibernate, remaining dormant throughout the winter in attics,
around chimneys, and in sheltered but cold situations. This belief
•has been challenged by Skinner (1913), who maintains that all the
adult flies die off during the fall and early winter and that the species
is carried over in the pupal stage, and in no other way. The cluster-
fly, Pollenia rudis, undoubtedly does hibernate in attics and similar

108. The house or typhoid fly (Musca domestica ( 4 .x)). After Howard.

situations and is often mistaken for the house-fly. In so far as
concerns Musca domestica, the important question as to hibernation
in the adult stage is an open one. Many observations by one of the
writers (Johannsen) tend to confirm Dr. Skinner’s conclusion, in so
far as it applies to conditions in the latitude of New York State.
Opposed, is the fact that various experimentors, notably Hewitt
(1910) and Jepson (1909) wholly failed to carry pupae through the
winter.

The house-fly breeds by preference in horse manure. Indeed,
Dr. Howard, whose extensive studies of the species especially qualify
him for expressing an opinion on the subject, has estimated that under
ordinary city and town conditions, more than ninety per cent of the
flies present in houses have come from horse stables or their vicinity.
They are not limited to such localities, by any means, for it has been
found that they would develop in almost any fermenting organic
substance. Thus, they have been bred from pig, chicken, and cow

148 Arthropods as Simple Carriers of Disease

manure, dirty waste paper, decaying vegetation, decaying meat,
slaughter-house refuse, sawdust-sweepings, and many other sources.
A fact which makes them especially dangerous as disease-carriers
is that they breed readily in human excrement.

The eggs are pure white, elongate ovoid, somewhat broader at
the anterior end. They measure about one millimeter (1-25 inch)
in length. They are deposited in small, irregular clusters, one
hundred and twenty to one hundred and fifty from a single fly. A
female may deposit as many as four batches in her life time. The
eggs hatch in from eight to twenty-four hours.

The newly hatched larva, or maggot (fig. 108), measures about two
millimeters (1-12 inch) in length. It is pointed at the head end and
blunt at the opposite end, where the spiracular openings are borne.
It grows rapidly, molts three times and reaches maturity in from six
to seven days, under favorable conditions.

The pupal stage, like that of related flies, is passed in the old
larval skin which, instead of being molted, becomes contracted and
heavily chitinized, forming the so-called puparium (fig. 108). The
pupal stage may be completed in from three to six days.

Thus during the warm summer months a generation of flies may
be produced in ten to twelve days. Hewitt at Manchester, England,
found the minimum to be eight days but states that larvas bred in
the open air in horse manure which had an average daily temperature
of 22.5 C., occupied fourteen to twenty days in their development,
according to the air temperature.

After emergence, a period of time must elapse before the fly is
capable of depositing eggs. This period has been termed the pre-
oviposition period. Unfortunately we have few exact data regarding
this period. Hewitt found that the flies became sexually mature in
ten to fourteen days after their emergence from the pupal state and
four days after copulation they began to deposit their eggs ; in other
words the preoviposition stage was fourteen days or longer. Griffith
(1908) found this period to be ten days. Dr. Howard believes that
the time “must surely be shorter, and perhaps much shorter, under
midsummer conditions, and in the freedom of the open air.’’ He
emphasizes that the point is of great practical importance, since it is
during this period that the trapping and other methods of destroying
the adult flies, will prove most useful.

Howard estimates that there may be nine generations of flies a
year under outdoor conditions in places comparable in climate to

The House-fly as a Carrier of Disease 149

Washington. The number may be considerably increased in warmer
climates.

The rate at which flies may increase under favorable conditions is
astounding. Various writers have given estimates of the numbers of
flies which may develop as the progeny of a single individual, provid¬
ing all the eggs and all the individual flies survived. Thus, Howard
estimates that from a single female, depositing one hundred and
twenty eggs on April 15th, there may be by September 10th,
5,598,720,000,000 adults. Fortunately, living forms do not produce
in any such mathematical manner and the chief value of the figures
is to illustrate the enormous struggle for existence which is con¬
stantly taking place in nature.

Flies may travel for a considerable distance to reach food and
shelter, though normally they pass to dwellings and other sources
of food supply in the immediate neighborhood of their breeding
places. Copeman, Howlett and Merriman (1911) marked flies by
shaking them in a bag containing colored chalk. Such flies were
repeatedly recovered at distances of eight to one thousand yards
and even at a distance of seventeen hundred yards, nearly a mile.

Hindle and Merriman (1914) continued these experiments on a
large scale at Cambridge, England. They “do not think it likely
that, as a rule, flies travel more than a quarter of a mile in thickly-
housed areas.” In one case a single fly was recovered at a distance
of 770 yards but a part of this distance was across open fen-land.
The surprising fact was brought out that flies tend to travel either
against or across the wind. The actual direction followed may be
determined either directly by the action of the wind (positive anemo-
tropism), or indirectly owing to the flies being attracted by any odor
that it may convey from a source of food. They conclude that it is
likely that the chief conditions favoring the disposal of flies are fine
weather and a warm temperature. The nature of the locality is
another considerable factor. Hodge (1913) has shown that when
aided by the wind they may fly to much greater distances over the
water. He reports that at Cleveland, Ohio, the cribs of the water
works, situated a mile and a quarter, five miles, and six miles out in
Lake Erie are invaded by a regular plague of flies when the wind
blows from the city. Investigation showed that there was absolutely
nothing of any kind in which flies could breed on the crib.

The omnivorous habits of the house-fly are matters of everyday
observation. From our view point, it is sufficient to emphasize

150 Arthropods as Simple Carriers of Disease

that from feeding on excrement, on sputum, on open sores, or on
putrifying matter, the flies may pass to the food or milk upon the table
or to healthy mucous membranes, or uncontaminated wounds.
There is nothing in its appearance to tell whether the fly that comes
blithely to sup with you is merely unclean, or whether it has just
finished feeding upon dejecta teeming with typhoid bacilli.

109. Pulvillus of foot of house-fly, showing glandular hairs.

The method of feeding of the house-fly has an important bearing
on the question of its ability to transmit pathogenic organisms.
Graham-Smith (1910) has shown that when feeding, flies frequently
moisten soluble substances with “vomit” which is regurgitated from
the crop. This is, of course, loaded with bacteria from previous
food. When not sucked up again these drops of liquid dry, and pro¬
duce round marks with an opaque center and rim and an intervening
less opaque area. Fly-specks, then, consist of both vomit spots
and feces. Graham-Smith shows a photograph of a cupboard window
where, on an area six inches square, there were counted eleven hundred
and two vomit marks and nine fecal deposits.

The House-fly as a Carrier of Disease 151

From a bacteriologist’s viewpoint a discussion of the possibility
of a fly’s carrying bacteria would seem superfluous. Any exposed
object, animate or inanimate, is contaminated by bacteria and will
transfer them if brought into contact with suitable culture media,
whether such substance be food, or drink, open wounds, or the sterile
culture media of the laboratory. A needle point may convey enough
germs to produce disease. Much more readily may the house-fly
with its covering of hairs and its sponge-like pulvilli (fig. 109) pick
up and transfer bits of filth and other contaminated material.

For popular instruction this inevitable transfer of germs by the
house-fly is strikingly demonstrated by the oft copied illustration
of the tracks of a fly on a sterile culture plate. Two plates of gela¬
tine or, better, agar medium are prepared. Over one of these a fly
(with wings clipped) is allowed to walk, the other is kept as a check.
Both are put aside at room temperature, to be examined after twenty-
four to forty-eight hours. At the end of that time, the check plate
is as clear as ever, the one which the fly has walked is dotted with
colonies of bacteria and fungi. The value in the experiment consists
in emphasizing that by this method we merely render visible what is
constantly occurring in nature.

A comparable experiment which we use in our elementary labora¬
tory work is to take three samples of clean (preferably, sterile) fresh
milk in sterile bottles. One of them is plugged with a pledget of
cotton, into the second is dropped a fly from the laboratory and into
the third is dropped a fly which has been caught feeding upon gar¬
bage or other filth. After a minute or two the flies are removed and
the vials plugged as was number one. The three are then set aside
at room temperature. When examined after twenty-four hours
the milk in the first vial is either still sweet or has a “ clean” sour odor;
that of the remaining two is very different, for it has a putrid odor,
which is usually more pronounced in the case of sample number
three.

Several workers have carried out experiments to determine the
number of bacteria carried by flies under natural conditions. 'One
of the most extended and best known of these is the series by Esten
and Mason (1908). These workers caught flies from various sources
in a sterilized net, placed them in a sterile bottle and poured over
them a known quantity of sterilized water, in which they were shaken
so as to wash the bacteria from their bodies. They found the number
of bacteria on a single fly to range from 550 to 6,600,000. Early in

152

Arthropods as Simple Carriers of Disease

the fly season the numbers of bacteria on flies are comparatively
small, while later the numbers are comparatively very large. The
place where flies live also determines largely the numbers that they
carry. The lowest number, 550, was from a fly caught in the
bacteriological laboratory, the highest number, 6,600,000 was the
average from eighteen swill-barrel flies. Torrey (1912) made exami¬
nation of “wild” flies from a tenement house district of New York
City. He Hound “that the surface contamination of these ‘wild’
flies may vary from 570 to 4,400,000 bacteria per insect, and the
intestinal bacterial content from 16,000 to 28,000,000.”

Less well known in this country is the work of Cox, Lewis, and
Glynn (1912). They examined over four hundred and fifty naturally
infected house-flies in Liverpool during September and early October.
Instead of washing the flies they were allowed to swim on the surface
of sterile water for five, fifteen, or thirty minutes, thus giving natural
conditions, where infection occurs from vomit and dejecta of the
flies, as well as from their bodies. They found, as might be expected,
that flies from either insanitary or congested areas of the city contain
far more bacteria than those from the more sanitary, less congested,
or suburban areas. The number of aerobic bacteria from the former
varied from 800,000 to 500,000,000 per fly and from the latter from
21,000 to 100,000. The number of intestinal forms conveyed by
flies from insanitary or congested areas was from 10,000 to 333,000,000
as compared with from 100 to 10,000 carried by flies from the more
sanitary areas.

Pathogenic bacteria and those allied to the food poisoning group
were only obtained from the congested or moderately congested
areas and not from the suburban areas, where the chances of infesta¬
tion were less.

The interesting fact was brought out that flies caught in milk
shops apparently carry and obtain more bacteria than those from
other shops with exposed food in a similar neighborhood. The
writers explained this as probably due to the fact that milk when
accessible, especially during the summer months, is suitable culture
medium for bacteria, and the flies first inoculate the milk and later
reinoculate themselves, and then more of the milk, so establishing a
vicious circle.

They conclude that in cities where food is plentiful flies rarely
migrate from the locality in which they arc bred, and consequently
the number of bacteria which they carry depends upon the general

The House-fly as a Carrier of Disease

i53

standard of cleanliness in that locality. Flies caught in a street of
modem, fairly high class, workmen’s dwellings forming a sanitary
oasis in the midst of a slum area, carried far less bacteria than those
caught in the adjacent neighborhood.

Thus, as the amount of dirt carried by flies in any particular
locality, measured in the terms of bacteria, bears a definite relation
to the habits of the people and to the state of the streets, it demon¬
strates the necessity of efficient municipal and domestic cleanliness,
if the food of the inhabitants is to escape pollution, not only with
harmless but also with occasional pathogenic bacteria.

The above cited w T ork is of a general nature, but, especially in
recent years, many attempts have been made to determine more
specifically the ability of flies to transmit pathogenic organisms.
The critical reviews of Nuttall and Jepson (1909), Howard (1911),
and Graham-Smith (1913) should be consulted by the student of
the subject. We can only cite here a few of the more striking experi¬
ments.

Celli (1888) fed flies on pure cultures of Bacillus typhosus and de¬
clared that he was able to recover these organisms from the intestinal
contents and excrement.

Firth and Horrocks (1902), cited by Nuttall and Jepson, “kept
Musca domestica (also bluebottles) in a large box measuring 4x3x3
feet, with one side made of glass. They were fed on material
contaminated u r ith cultures of B. typhosus. Agar plates, litmus,
glucose broth and a sheet of clean paper were at the same time
exposed in the box. After a few days the plates and broth were
removed and incubated with a positive result.” Graham-Smith
(1910) “carried out experiments with large numbers of flies kept
in gauze cages and fed for eight hours on emulsions of B. typhosus
in syrup. After that time the infested syrup was removed and the
flies were fed on plain syrup. B. typhosus was isolated up to 48
horns (but not later) from emulsions of their feces and from plates
over w r hich they walked.”

Several other w r orkers, notably Hamilton (1903), Ficker (1903),
Bertarelli (1910) Faichnie (1909), and Cochrane (1912), have iso¬
lated B. typhosus from “wild” flies, naturally infected. The papers
of Faichnie and of Cochrane we have not seen, but they are quoted
in extenso by Graham-Smith (1913).

On the whole, the evidence is conclusive that typhoid germs not
only may be accidentally carried on the bodies of house-flies but

154

Arthropods as Simple Carriers of Disease

may pas's through their bodies and be scattered in a viable condition
in the feces of the fly for at least two days after feeding. Similar,
results have been reached in experiments with cholera, tuberculosis
and yaws, the last-mentioned being a spirochaete disease. Darling
(1913) has shown that murrina, a trypanosome disease of horses
and mules in the Canal zone is transmitted by house-flies which feed
upon excoriated patches of diseased animals and then pass to cuts
and galls of healthy animals.

Since it is clear that flies are abundantly able to disseminate
viable pathogenic bacteria, it is important to consider whether they
have access to such organisms in nature. A consideration of the
method of spread of typhoid will serve to illustrate the way in which
flies may play an important r 61 e.

Typhoid fever is a specific disease caused by Bacillus typhosus ,
and by it alone. The causative organism is to be found in the excre¬
ment and urine of patients suffering from the disease. More than
that, it is often present in the dejecta for days, weeks, or even months
and years, after the individual has recovered from the disease.
Individuals so infested are known as “typhoid carriers” and they,
together with those suffering from mild cases, or “walking typhoid,”
are a constant menace to the health of the community in which they
are found.

Human excrement is greedily visited by flies, both for feeding and
for ovipositing. The discharges of typhoid patients, or of chronic
“carriers,” when passed in the open, in box privies, or camp latrines,
or the like, serve to contaminate myriads of the insects which may
then spread the germ to human food and drink. Other intestinal
diseases may be similarly spread. There is abundant epidsemiologi-
cal evidence that infantile diarrhoea, dysentery, and cholera may be
so spread.

Stiles and Keister (1913) have shown that spores of Lamblia
intestinalis, a flagellate protozoan living in the human intestine,
may be carried by house-flies. Though this species is not normally
pathogenic, one or more species of Entamoeba are the cause of a type
of a highly fatal tropical dysentery. Concerning it, and another
protozoan parasite of man, they say, “If flies can carry Lamblia
spores measuring 10 to 7 [jl, and bacteria that arc much smaller, and
particles of lime that arc much larger, there is no ground to assume
that flies may not carry Entamoeba and Trichomonas spores.

The House-fly as a Carrier of Disease

155

Tuberculosis is one of the diseases which it is quite conceivable
may be carried occasionally. The spurirm of tubercular patients
is very attractive to flies, and various workers, notably Graham-
Smith, have found that Musca domestica may distribute the bacillus
for several days after feeding on infected material.

A type of purulent opthalmia which is very prevalent in Egypt
is often said to be carried by flies. Nuttall and Jepson (1909)
consider that the evidence regarding the spread of this disease by
flies is conclusive and that the possibility of gonorrhoeal secretions
being likewise conveyed cannot be denied.

Many studies have been published, showing a marked agreement
between the occurrence of typhoid and other intestinal diseases
and the prevalence of house-flies. The most clear-cut of these are
the studies of the Army Commission appointed to investigate the
cause of epidemics of enteric fever in the volunteer camps in the
Southern United States during the Spanish-American War. Though
their findings as presented by Vaughan (1909), have been quoted
very many times, they are so germane to our discussion that they
will bear repetition:

“Flies swarmed over infected fecal matter in the pits and fed
upon the food prepared for the soldiers in the mess tents. In some
instances where lime had recently been sprinkled over the contents
of the pits, flies with their feet whitened with lime were seen walking
over the food.” Under such conditions it is no wonder that “These
pests had inflicted greater loss upon American soldiers than the arms
of Spain.”

Similar conditions prevailed in South Africa during the Boer War.
Seamon believes that very much of the success of the Japanese in
their fight against Russia was due to the rigid precautions taken to
prevent the spread of disease by these insects and other means.

Veeder has pointed out that the characteristics of a typical fly-
borne epidemic of typhoid are that it occurs in little neighborhood
epidemics, extending by short leaps from house to house, without
regard to water supply or anything else in common. It tends to
follow the direction of prevailing winds (cf. the conclusions of Hindle
and Merriman). It occurs during warm weather. Of course, when
the epidemic is once well under way, other factors enter into its spread.

In general, flies may be said to be the chief agency in the spread of
typhoid in villages and camps. In cities with modern sewer systems
they are less important, though even under the best of such condi-

156 Arthropods as Simple Carriers of Disease

tions, they are important factors. Howard has emphasized that in
such cities there are still many uncared-for box privies and that, in
addition, the deposition of feces overnight in uncared-for waste lots
and alleys is common.

Not only unicellular organisms, such as bacteria and protozoa,
but also the eggs, embryos and larvae of parasitic worms have been
found to be transported by house-flies. Ransom (1911) has found
that Habronema muscce, a nematode worm often found in adult flies,
is the immature stage of a parasite occurring in the stomach of the
horse. The eggs or embryos passing out with the feces of the horse,
are taken up by fly larvae and carried over to the imago stage.

Grassi (1883), Stiles (1889), Calandruccio (1906), and especially
Nicoll (1911), have been the chief investigators of the ability of
house-flies to carry the ova and embryos of human intestinal parasites.
Graham-Smith (1913) summarizes the work along this line as follows:

“It is evident from the investigations that have been quoted that
house-flies and other species are greatly attracted to the ova of
parasitic worms contained in feces and other materials, and make
great efforts to ingest them. Unless the ova are too large they often
succeed, and the eggs are deposited uninjured in their feces, in some
cases up to the third day at least. The eggs may also be carried on
their legs or bodies. Under suitable conditions, food and fluids
may be contaminated with the eggs of various parasitic worms by flies,
and in one case infection of the human subject has been observed.
Feces containing tape-worm segments may continue to be a source of
infection for as long as a fortnight. Up to the present, however,
there is no evidence to show what part flies play in the dissemination
of parasitic worms under natural conditions.”

Enough has been said to show that the house-fly must be dealt
with as a direct menace to public health. Control measures are
not merely matters of convenience but are of vital importance.

Under present conditions the speedy elimination of the house-fly
is impossible and the first thing to be considered is methods of pro¬
tecting food and drink from contamination. The first of these
methods is the thorough screening of doors and windows to prevent
the entrance of flies. In the case of kitchen doors, the flies, attracted
by odors, are likely to swarm onto the screen and improve the first
opportunity for gaining an entrance. This difficulty can be largely
avoided by screening-in the back porch and placing the screen door
at one end rather than directly before the door.

The House-fly as a Carrier of Disease # 157

The use of sticky fly paper to catch the pests that gain entrance
to the house is preferable to the various poisons o£ten used. Of the
latter, formalin (40 per cent formaldehyde) in the proportion of two
tablespoonfuls to a pint of water is very efficient, if all other liquids
are removed or covered, so that the flies must depend on the formalin
for drink. The mixture is said to be made more attractive by the
addition of sugar or milk, though we have found the plain solution
wholly satisfactory, under proper conditions. It should be em¬
phasized that this formalin mixture is not perfectly harmless, as so
often stated. There are on record cases of severe and even fatal
poisoning from the accidental drinking of solutions.

When flies are very abundant in a room they can be most readily
gotten rid of by fumigation with sulphur, or by the use of pure
pyrethrum powder either burned or puffed into the air. Herrick
(1913) recommends the following method: “At night all the doors
and windows of the kitchen should be closed; fresh powder should
be sprinkled over the stove, on the window ledges, tables, and in the
air. In the morning flies will be found lying around dead or stupified.
They may then be swept up and burned.” This method has proved
very efficaceous in some of the large dining halls in Ithaca.

The writers have had little success in fumigating with the vapors
of carbolic acid, or carbolic acid and gum camphor, although these
methods will aid in driving flies from a darkened room.

All of these methods are but makeshifts. As Howard has so well
put it, “the truest and simplest way of attacking the fly problem
is to prevent them from breeding, by the treatment or abolition of
all places in which they can breed. To permit them to breed un¬
disturbed and in countless numbers, and to devote all our energy to
the problem of keeping them out of our dwellings, or to destroy them
after they have once entered in spite of all obstacles, seems the
wrong way to go about it.”

We have already seen that Musca doniestica breeds in almost any
fermenting organic material. While it prefers horse manure, it
breeds also in human feces, cow dung and that of other animals,
and in refuse of many kinds. To efficiently combat the insect,
these breeding places must be removed or must be treated in some
such way as to render them unsuitable for the development of the
larvae. Under some conditions individual work may prove effective,
but to be truly efficient there must be extensive and thorough co¬
operative efforts.

158 Arthropods as Simple Carriers of Disease

Manure, garbage, and the like should be stored in tight receptacles
and carted away at least once a week. The manure may be carted
to the fields and spread. Even in spread manure the larvae may con¬
tinue their development. Howard points out that “it often happens
that after a lawn has been heavily manured in early summer the
occupants of the house will be pestered with flies for a time, but
finding no available breeding place these disappear sooner or later.
Another generation will not breed in the spread manure.”

Hutchinson (1914) has emphasized that the larvae of house¬
flies have deeply engrained the habit of migrating in the prepupal
stage and has shown that this offers an important point of attack
in attempts to control the pest. He has suggested that maggot
traps might be developed into an efficient weapon in the warfare
against the house-fly. Certain it is that the habit greatly simplifies the
problem of treating the manure for the purpose of killing the larvae.

There have been many attempts to find some cheap chemical
which would destroy fly larvae in horse manure without injuring the
bacteria or reducing the fertilizing values of the manure.. The litera¬
ture abounds in recommendations of kerosene, lime, chloride of lime,
iron sulphate, and other substances, but none of them have met the
situation. The whole question has been gone into thoroughly by
Cook, Hutchinson and Scales (1914), who tested practically all of the
substances which have been recommended. They find that by far
the most effective, economical, and practical of the substances is
borax in the commercial form in which it is available throughout the
•country.

“Borax increases the water-soluble nitrogen, ammonia and alkali¬
nity of manure and apparently does not permanently injure the
bacterial flora. The application of manure treated with borax at the
rate of 0.62 pound per eight bushels (10 cubic feet) to soil does not
injure the plants thus far tested, although its cumulative effect, if
.any, has not been determined.”

As their results clearly show that the substances so often recom¬
mended are inferior to borax, we shall quote in detail their directions
for treating manure so as to kill fly eggs and maggots.

“Apply 0.62 pound borax or 0.75 pound calcined colemanite to
•every 1 o cubic feet (8 bushels) of manure immediately on its removal
from the barn. Apply the borax particularly around the outer
edges of the pile with a flour sifter or any fine sieve, and sprinkle two
■or three gallons of water over the borax-treated manure.

The House-fly as a Carrier of Disease

i59

“The reason for applying the borax to the fresh manure immedi¬
ately after its removal from the stable is that the flies lay their eggs
on the fresh manure, and borax, when it comes in contact with the
eggs, prevents their hatching. As the maggots congregate at the
outer edge of the pile, most of the borax should be applied there.
The treatment should be repeated with each addition of fresh manure,
but when the manure is kept in closed boxes, less frequent applica¬
tions will be sufficient. When the calcined colemanite is available,
it may be used at the rate of 0.75 pound per 10 cubic feet of manure,
and is a cheaper means of killing the maggots. In addition to the
application of borax to horse manure to kill fly larvae, it may be
applied in the same proportion to other manures, as well as to refuse
and garbage. Borax may also be applied to the floors and crevices in
bams, stables, markets, etc., as well as to street sweepings, and water
should be added as in the treatment of horse manure. After estimat¬
ing the amount of material to be treated and weighing the necessary’
amount of borax, a measure may be used which will hold the proper
amount, thus avoiding the subsequent weighings.

“While it can be safely stated that no injurious action will follow
the application of manure treated with borax at the rate of 0.62
pound for eight bushels, or even larger amounts in the case of some
plants, nevertheless the borax-treated manure has not been studied
in connection with the growth of all crops, nor has its cumulative
effect been determined. It is therefore recommended that not more
than 15 tons per acre of the borax-treated manure should be applied
to the field. As truckmen use considerably more than this amount,
it is suggested that all cars containing borax-treated manure be so
marked, and that public-health officials stipulate in their directions
for this treatment that not over 0.62 pound for eight bushels of manure
be used, as it has been shown that larger amounts of borax will
injure most plants. It is also recommended that all public-health
officials and others, in recommending the borax treatment for kill¬
ing fly eggs and maggots in manure, warn the public against the
injurious effects of large amounts of borax on the growth of plants.”

“The amount of manure from a horse varies with the straw or
other bedding used, but 12 or 15 bushels per week represent the
approximate amount obtained. As borax costs from five to six
cents per pound in ioo-pound lots in Washington, it will make the
cost of the borax practically one cent per horse, per day. And if
calcined colemanite is purchased in large shipments the cost should
be considerably less.”

160 Arthropods as Simple Carriers of Disease

Hodge (1910) has approached the problem of fly extermination
from another viewpoint. He believes that it is practical to trap
flies out of doors during the preoviposition period, when they are
sexually immature, and to destroy such numbers of them that the
comparatively few which survive will not be able to lay eggs in suffi-
cent numbers to make the next generation a nuisance. To the end
of capturing them in enormous numbers he has devised traps to be
fitted over garbage cans, into stable windows, and connected with the
kitchen window screens. Under some conditions this method of
attack has proved very satisfactory.

One of the most important measures for preventing the spread
of disease by flies is the abolition of the common box privy. In
villages and rural districts this is today almost the only type to be
found. It is the chief factor in the spread of typhoid and other
intestinal diseases, as well as intestinal parasites. Open and ex¬
posed to myriads of flies which not only breed there but which feed
upon the excrement, they furnish ideal conditions for spreading con¬
tamination. Even where efforts are made to cover the contents
with dust, or ashes, or lime, flies may continue to breed unchecked.
Stiles and Gardner have shown that house-flies buried in a screened
stand-pipe forty-eight inches under sterile sand came to the surface.
Other flies of undetermined species struggled up through seventy-
two inches of sand.

So great is the menace of the ordinary box privy that a number of
inexpensive and simple sanitary privies have been designed for use
where there are not modem sewer systems. Stiles and Lumsden
(1911) have given minute directions for the construction of one of the
best types, and their bulletin should be obtained by those interested.

Another precaution which is of fundamental importance in
preventing the spread of typhoid, is that of disinfecting all discharges
from patients suffering with the disease. For this purpose, quick¬
lime is the cheapest and is wholly satisfactory. In chamber vessels
it should be used in a quantity equal to that of the discharge to be
treated. It should be allowed to act for two hours. Air-slaked
lime is of no value whatever. Chloride of lime, carbolic acid, or
formalin may be used, but are more expensive. Other intestinal
diseases demand similar precautions.

Stomoxys calcitrans, the stable-fly— It is a popular belief that
house-flies bite more viciously just before a rain. As a matter of

Stomoxys calcitrans, the Stable-fly

161

fact, the true house-flies never bite, for their mouth-parts are not
fitted for piercing. The basis of the misconception is the fact that a
true biting fly, Stomoxys calcitrans (fig. no), closely resembling the
house-fly, is frequently found in houses and may be driven in in
greater numbers by muggy weather. From its usual habitat this
fly is known as the “stable-fly” or, sometimes as the “biting house¬
fly.”

Stomoxys calcitrans may be separated from the house-fly by the use
of the key on p. 145. It may be more fully characterized as follows:

The eyes of the male are separated by a distance equal to one-
fourth of the diameter of the head, in the female by one-third. The

110. Stomoxys calcitrans; adult, larva, puparium and details. (x5). After Howard.

frontal stripe is black, the cheeks and margins of the orbits silvery-
white. The antennae are black, the arista feathered on the upper
side only. The proboscis is black, slender, fitted for piercing and
projects forward in front of the head. The thorax is grayish, marked
by four conspicuous, more or less complete black longitudinal stripes;
the scutellum is paler; the macrochaetas are black. The abdomen is
gray, dorsally with three brown spots on the second and third seg¬
ments and a median spot on the fourth. These spots are more
pronounced in the female. The legs are black, the pulvilli distinct.
The wings are hyaline, the vein Mi + 2 less sharply curved than in
the house-fly, the apical cell being thus more widely open (cf. fig.
no). Length 7 mm.

This fly is widely distributed, being found the world over. It was
probably introduced into the United States, but has spread to all

162

Arthropods as Simple Carriers of Disease

parts of the country. Bishopp (1913) regards it as of much more
importance as a pest of domestic animals in the grain belt than else¬
where in the United States. The life-history and habits of this
species have assumed a new significance since it has been suggested
that it may transmit the human diseases, infantile paralysis and
pellagra. In this country, the most detailed study of the fly is that
of Bishopp (1913) whose data regarding the life cycle are as follows:

The eggs like those of the house-fly, are about one mm.
in length. Under a magnifying glass they show a distinct furrow
along one side. When placed on any moist substance they hatch
in from one to three days after being deposited.

The larvae or maggots (fig. 110) have the typical shape and actions
of most maggots of the Museid group. They can be distinguished
from those of the house-fly as the stigma-plates are smaller, much
further apart, with the slits less sinuous. Development takes place
fairly rapidly when the proper food conditions are available and
the growth is completed within eleven to thirty or more days.

The pupa (fig. no), like that of related flies, undergoes its develop¬
ment within the contracted and hardened last larval skin, or pu-
parium. This is elongate oval, slightly thicker towards the head end,
and one-sixth to one-fourth of an inch in length. The pupal stage
requires six to twenty days, or in cool weather considerably longer.

The life-cycle of the stable-fly is therefore considerably longer
than that of Musca domestica. Bishopp found that complete
development might be undergone in nineteen days, but that the
average period was somewhat longer, ranging from twenty-one to
twenty-five days, where conditions are very favorable. The longest
period which he observed was forty-three days, though his finding
of full grown larvae and pupae in straw during the latter part of
March, in Northern Texas, showed that development may require
about three months, as he considered that these stages almost cer¬
tainly developed from eggs deposited the previous December.

The favorite breeding place, where available, seems to be straw or
manure mixed with straw. It also breeds in great numbers in horse-
manure, in company with Musca domestica.

Ncwstead considers that in England the stable-fly hibernates in
the pupal stage. Bishopp finds that in the southern part of the
United States there is no true hibernation, as the adults have been
found to emerge at various times during the winter. He believes
that in the northern United States the winter is normally passed

Other Arthropods as Simple Carriers

163

in the larval and pupal stages, and that the adults which have been
observed in heated stables in the dead of winter were bred out in
refuse within the warm bams and were not hibernating adults.

Graham-Smith (1913) states that although the stable-fly fre¬
quents stable manure, it is probably not an important agent in
distributing the organisms of intestinal diseases. Bishopp makes the
important observation that “it has never been found breeding in
human excrement and does not frequent malodorous places, which
are so attractive to the house-fly. Hence it is much less likely to
carry typhoid and other germs which may be found in such places.”

Questions of the possible agency of Stomoxys calcitrans in the trans¬
mission of infantile paralysis and of pellagra, we shall consider later.

Other arthropods which may serve as simple carriers of patho¬
genic organisms —It should be again emphasized that any insect which
has access to, and comes in contact with, pathogenic organisms
and then passes to the food, or drink, or the body of man, may serve
as a simple carrier of disease. In addition to the more obvious
illustrations, an interesting one is the previously cited case of the
transfer of Dermatobia cyaniventris by a mosquito (fig. 81-84).
Darling (1913) has shown that in the tropics, the omnipresent ants
may be important factors in the spread of disease.

CHAPTER VI

ARTHROPODS AS DIRECT INOCULATORS OF DISEASE GERMS

We have seen that any insect which, like the house-fly, has access
to disease germs and then comes into contact with the food or drink
of man, may serve to disseminate disease. Moreover, it has been
clearly established that a contaminated insect, alighting upon
wounded or abraded surfaces, may infect them. These are instances
of mere accidental, mechanical transfer of pathogenic organisms.

Closely related are the instances of direct inoculation of disease
germs by insects and other arthropods. In this type, a blood¬
sucking species not only takes up the germs but, passing to a healthy
individual, it inserts its contaminated mouth-parts and thus directly
inoculates its victim. In other words, the disease is transferred
just as blood poisoning may be induced by the prick of a contami¬
nated needle, or as the laboratory worker may inoculate an experi¬
mental animal.

Formerly, it was supposed that this method of the transfer of
disease by arthropods was a very common one and many instances
are cited in the earlier literature of the subject. It is, however,
difficult to draw a sharp line between such cases and those in which,
on the one hand, the arthropod serves as a mere passive carrier or,
on the other hand, serves as an essential host of the pathogenic
organism. More critical study of the subject has led to the belief
that the importance of the role of arthropods as direct inoculators
has been much overestimated.

The principal reason for regarding this phase of the subject as
relatively unimportant, is derived from a study of the habits of the
blood-sucking species. It is found that, in general, they are inter¬
mittent feeders, visiting their hosts at intervals and then abstaining
from feeding for a more or less extended period, while digesting their
meal. In the meantime, most species of bacteria or of protozoan
parasites with which they might have contaminated their mouth-
parts, would have perished, through inability to withstand drying.

In spite of this, it must be recognized that this method of transfer
does occur and must be reckoned with in any consideration of the
relations of insects to disease. We shall first cite some general
illustrations and shall then discuss the role of fleas in the spreading
of bubonic plague, an illustration which cannot be regarded as typi¬
cal, since it involves more than mere passive carnage.

Some Illustrations of Direct Inoculation 165

Some Illustrations of Direct Inoculation of Disease Germs

by Arthropods

In discussing poisonous arthropods, we have already emphasized
that species which are of themselves innocuous to man, may occasion¬
ally introduce bacteria by their bite or sting and thus cause more or
less severe secondary symptoms. That such cases should occur, is
no more than is to be expected. The mouth-parts or the sting of
the insect are not sterile and the chances of their carrying pyogenic
organisms are always present.

More strictly falling in the category of transmission of disease
germs by direct inoculation are the instances where the insect, or
related form, feeds upon a diseased animal and passes promptly to a
healthy individual which it infects. Of such a nature are the follow¬
ing:

Various species of biting flies are factors in the dissemination of
anthrax, an infectious and usually fatal disease of animals and,
occasionally, of man. That the bacteria with which the blood of
diseased animals teem shortly before death might be transmitted
by such insects has long been contended, but the evidence in support
of the view has been unsatisfactory. Recently, Mitzmain (1914)
has reported a series of experiments which show conclusively that the
disease may be so conveyed by a horse-fly, Tabanus striatus, and by
the stable-fly, Stomoxys calcitrans.

Mitzmain’s experiments were tried with an artificially infected
guinea pig, which died of the disease upon the third day. The flies
were applied two and one-half hours, to a few minutes, before the
death of the animal. With both species the infection was success¬
fully transferred to healthy guinea pigs by the direct method, in
which the flies were interrupted while feeding on the sick animal.
The evidence at hand does not warrant the conclusion that insect
transmission is the rule in the case of this disease.

The nagana, or tsetse-fly disease of cattle is the most virulent
disease of domestic animals in certain parts of Africa. It is caused
by a protozoan blood parasite, Trypanosoma brucei, which is con¬
veyed to healthy animals by the bite of Glossina morsitans and possi¬
bly other species of tsetse-flies. The flies remain infective for
forty-eight hours after feeding on a diseased animal. The insect
also serves as an essential host of the parasite.

Surra, a similar trypanosomiasis affecting especially horses and
mules, occurs in southern Asia, Malaysia, and the Philippines where

166 Arthropods as Direct Inoculators of Disease Germs

the tsetse-flies are not to be found. It is thought to be spread by
various species of blood-sucking flies belonging to the genera Stomoxys,
Hcematobia, and Tabanus. Mitzmain (1913) demonstrated that in
the Philippines it is conveyed mechanically by Tabanus striatus.

The sleeping sickness of man, in Africa, has also been supposed
to be directly inoculated by one, or several, species of tsetse-flies.
It is now known that the fly may convey the disease for a short
time after feeding, but that there is then a latent period of from
fourteen to twenty-one days, after which it again becomes infectious.
This indicates that in the meantime the parasite has been under¬
going some phase of its life-cycle and that the fly serves as an inter¬
mediate host. We shall therefore consider it more fully under that
grouping.

These are a few of the cases of direct inoculation which may be
cited as of the simpler type. We shall next consider the rdle of the
flea in the dissemination of the bubonic plague, an illustration
complicated by the fact that the bacillus multiples within the insect
and may be indirectly inoculated.

The Role of Fleas in the Transmission of the Plague

The plague is a specific infectious disease caused by Bacillus pestis.
It occurs in several forms, of which the bubonic and the pneumonic
are the most common. According to Wyman, 80 per cent of the
human cases are of the bubonic type. It is a disease which, under
the name of oriental plague, the pest, or the black death, has ravaged
almost from time immemorial the countries of Africa, Asia, and
Europe. The record of its ravages are almost beyond belief. In 542
A. D. it caused in one day ten thousand deaths in Constantinople.
In the 14th century it was introduced from the East and prevailed
throughout Armenia, Asia Minor, Egypt and Northern Africa and
Europe. Hecker estimates that one-fourth of the population of
Europe, or twenty-five million persons, died in the epidemic of that
century. From then until the 17th century it was almost constantly
present in Europe, the great plague of London, in 1665 killing 68,596
out of a population of 460,000. Such an epidemic would mean for
New York City a proportionate loss of over 600,000 in a single year.
It is little wonder that in the face of such an appalling disaster sus¬
picion and credulity were rife and the wildest demoralization ensued.

During the 14th century the Jews were regarded as responsible
for the disease, through poisoning wells, and were subjected to the

Role of Fleas in the Transmission of Plague

111. A contemporaneous engraving of the pest hospital in Vienna in 1679 .

After Peters.

most incredible persecution and torture. In Milan the visitation
of 1630 was credited to the so-called anointers, — men who were
supposed to spread the plague by anointing the walls with magic
ointment — and the most horrible tortures that human ingenuity
could devise were imposed on scores of victims, regardless of rank
or of public service (fig. ii2,a). Manzoni’s great historical novel,
“The Betrothed” has well pictured conditions in Italy during this
period.

In modem times the plague is confined primarily to warm climates,
a condition which has been brought about largely through general
improvement in sanitary conditions.

At present, the hotbed of the disease is India, where there were
1,040,429 deaths in 1904 and where in a period of fifteen years,
ending with January 1912, there were over 15,000,000 deaths. The
reported deaths in that country for 1913 totaled 198,875.

During the winter of 1910-11 there occurred in Manchuria and
North China a virulent epidemic of the pneumonic plague which
caused the death of nearly 50,000 people. The question as to its
origin and means of spread will be especially referred to later.

Until recent years, the plague had not been known to occur in
the New World but there were outbreaks in Brazil and Hawaii in
1899, and in 1900 there occurred the first cases in San Francisco.

i68

Arthropods as Direct Inoculators of Disease Germs

112 a. A medieval method of combating the plague. The persecution of the anointers in Milan in 1630 . From
copy of “II processi originale degli untori“ in the library of Cornell University.

Role of Fleas in the Transmission of Plague 169

In California there were 125 cases in the period 1900-04; three cases
in the next three years and then from May 1907 to March 1908,
during the height of the outbreak, 170 cases. Since that time there
have been only sporadic cases, the last case reported being in May
1914. Still more recent were the outbreaks in the Philippine Islands,
Porto Rico, and Cuba.

On June 24, 1914, there was recognized a case of human plague
in New Orleans. The Federal Health Service immediately took
charge, and measures for the eradication of the disease were vigor¬
ously enforced. Up to Otcober 10, 1914 there had been reported
30 cases of the disease in man, and 18 r cases of plague in rats.

112 b. The modern method of combating the plague. A day's catch of rats in the fight
against plague in San Francisco. Courtesy of Review of Reviews.

The present-day methods of combating bubonic plague are well
illustrated by the fight in San Francisco. Had it not been for the
strenuous and radical anti-plague campaign directed by the United
States Marine Hospital Service we might have had in our own
country an illustration of what the disease can accomplish. On what
newly acquired knowledge was this fight based?

The basis was laid in 1894, when the plague bacillus was first
discovered. All through the centuries, before and during the Christian
era, down to 1894, the subject was enveloped in darkness and there
had been a helpless, almost hopeless struggle in ignorance on the part
of physicians, sanitarians, and public health officials against the
ravages of this dread disease, Now its cause, method of propaga¬
tion and means to prevent its spread are matters of scientific cer¬
tainty.

170 Arthropods as Direct Inoculators of Disease Germs

After the discovery of the causative organism, one of the first
advances was the establishment of the identity of human plague
and that of rodents. It had often been noted that epidemics of the
human disease were preceded by great epizootics among rats and
mice. So well established was this fact that with the Chinese,
unusual mortality among these rodents was regarded as foretelling
a visitation of the human disease. That there was more than an
accidental connection between the two was obvious when Yersin,
the discoverer of Bacillus pestis, announced that during an epidemic
the rats found dead in the houses and in the streets almost always
contain the bacillus in great abundance in their organs, and that many
of them exhibit veritable buboes.

Once it was established that the diseases were identical, the atten¬
tion of the investigators was directed to a study of the relations
between that of rats and of humans, and evidence accumulated to
show that the bubonic plague was primarily a disease of rodents
and that in some manner it was conveyed from them to man.

There yet remained unexplained the method of transfer from rat
to man. As long ago as the 16th century, Mercuralis suggested
that house-flies were guilty of disseminating the plague but modem
investigation, while blaming the fly for much in the way of spreading
disease, show that it is an insignificant factor in this case.

Search for blood-sucking insects which would feed on both rodents
and man, and which might therefore be implicated, indicated that
the fleas most nearly met the conditions. At first it was urged that
rat fleas would not feed upon man and that the fleas ordinarily attack¬
ing man would not feed upon rats. More critical study of the habits
of fleas soon showed that these objections were not well-founded.
Especially important was the evidence that soon after the death of
their host, rat fleas deserted its body and might then become a pest
in houses "where they had not been noticed before.

Attention was directed to the fact that while feeding, fleas are in
the habit of squirting blood from the anus and that in the case of those
which had fed upon rats and mice dying of the plague, virulent plague
bacilli were to be found in such blood. Liston (1905) even found,,
and subsequent investigations confirmed, that the jflague bacilli
multiply in the stomach of the insect and that thus the blood ejected
was richer in the organisms than was that of the diseased animal.
It was found that a film of this infected blood spread out under the
body of the flea and that thus the bacilli might be inoculated by the
bite of the insect and by scratching.

Role of Fleas in the Transmission of Plague 171

Very recently, Bacot and Martin (1914) have paid especial
attention to the question of the mechanism of the transmission of
the plague bacilli by fleas. They believe that plague infested fleas
regurgitate blood through tlje mouth, and that under conditions
precluding the possibility of infection by dejecta, the disease may be
thus transmitted. The evidence does not seem sufficient to establish
that this is the chief method of transmission.

Conclusive experimental proof that fleas transmit the disease is
further available from a number of sources. The most extensive
series of experiments is that of the English Plague Commission in
India, which reported in 1906 that:

On thirty occasions a healthy rat contracted plague in sequence
of living in the neighborhood of a plague infected rat under cir¬
cumstances which prevented the healthy rat coming in contact with
either the body or excreta of the diseased animal.

In twenty-one experiments out of thirty-eight, healthy rats living
in flea-proof cages contracted plague when exposed to rat fleas
(.Xenopsylla cheopis ), collected from rats dead or dying of septicaemic
plague.

Close contact of plague-infected with healthy animals, if fleas
are excluded, does not give rise to an epizootic among the latter.
As the huts were never cleaned out, close contact included contact
with feces and urine of infected animals, and contact with, and eat¬
ing of food contaminated with feces and urine of infected animals,
as well as pus from open plague ulcers. Close contact of young,
even when suckled by plague-infected mothers, did not give the
disease to the former.

If fleas are present, then the epizootic, once started, spreads from
animal to animal, the rate of progress being in direct proportion to
the number of fleas.

Aerial infection was excluded. Thus guinea-pigs suspended in a
cage two feet above the ground did not contract the disease, while
in the same hut those animals allowed to run about and those placed
two inches above the floor became infected. It had previously
been found that a rat flea could not hop farther than about five
inches.

Guinea pigs and monkeys were placed in plague houses in pairs,
both protected from soil contact infection and both equally exposed
to aerial infection, but one surrounded with a layer of tangle-foot
paper and the other surrounded with a layer of sand. The follow¬
ing observations were made:

172 Arthropods as Direct Inoculators of Disease Germs

(a) Many fleas were caught in the tangle-foot, a certain pro¬
portion of which were found on dissection to contain in their stomachs
abundant bacilli microscopically identical with plague bacilli. Out
of eighty-five human fleas dissected only one contained these bacilli,
while out of seventy-seven rat fleas twenty-three were found thus
infected.

' ( b ) The animals surrounded with tangle-foot in no instance
developed plague, while several (24 per cent) of the non-protected
animals died of the disease.

Thus, the experimental evidence that fleas transmit the plague
from rat to rat, from rats to guinea pigs, and from rats to monkeys
is indisputable. There is lacking direct experimental proof of its
transfer from rodents to man but the whole chain of indirect evi¬
dence is so complete that there can be no doubt that such a transfer
does occur so commonly that in the case of bubonic plague it must
be regarded as the normal method.

Rats are not the only animals naturally attacked by the plague
but as already suggested, it occurs in various other rodents. In
California the disease has spread from rats to ground squirrels
(Otospermophilus beecheyi), a condition readily arising from the
frequency of association of rats with the squirrels in the neighbor¬
hood of towns, and from the fact that the two species of fleas found
on them are also found on rats. While the danger of the disease
being conveyed from squirrels to man is comparatively slight, the
menace in the situation is that the squirrels may become a more or
less permanent reservoir of the disease and infect rats, which may
come into more frequent contact with man.

The tarbagan (Arctomys bobac ), is a rodent found in North Man¬
churia, which is much prized for its fur. It is claimed that this ani¬
mal is extremely susceptible to the plague and there is evidence to
indicate that it was the primary source of the great outbreak of
pneumonic plague which occurred in Manchuria and North China
during the winter of 1910-11.

Of fleas, any species which attacks both rodents and man may be
an agent in the transmission of the plague. We have seen that in
India the species most commonly implicated is the rat flea, Xenopsylla
cheopis, (= Leemopsylla or Pulex cheopis) (fig. 89). This species has
also been found commonly on rats in San Francisco. The cat flea,
Ctenocephalus felis, the dog flea, Ctenocephalus cards, the human flea,
Pulex irritans, the rat fleas, Ceratophyllus fasciatus and Ctenopsyllus
musculi have all been shown to meet the conditions.

Role of Fleas in the Transmission of Plague 173

But, however clear the evidence that fleas are the most important
agent in the transfer of plague, it is a mistake fraught with danger
to assume that they are the only factor in the spread of the disease.
The causative organism is a bacillus and is not dependent upon any
insect for the completion of its development.

Therefore, any blood-sucking insect which feeds upon a plague
infected man or animal and then passes to a healthy individual,
conceivably might transfer the bacilli. Verjbitski (1908) has shown
experimentally that bed-bugs may thus convey the disease. Hertzog
found the bacilli in a head-louse, Pediculus humanus, taken from a
child which had died from the plague, and McCoy found them in a
louse taken from a plague-infected squirrel. On account of their
stationary habits, the latter insects could be of little significance in
spreading the disease.

Contaminated food may also be a source of danger. While this
source, formerly supposed to be the principal one, is now regarded as
unimportant, there is abundant experimental evidence to show that
it cannot be disregarded. It is believed that infection in this way
can occur only when there is some lesion in the alimentary canal.

Still more important is the proof that in pneumonic plague the
patient is directly infective and that the disease is spread from man
to man without any intermediary. Especially conclusive is the
evidence obtained by Drs. Strong and Teague during the Manchurian
epidemic of 1910-11. They found that during coughing, in pneu¬
monic plague cases, even when sputum visible to the naked eye is
not expelled, plague bacilli in large numbers may become widely
disseminated into the surrounding air. By exposing sterile plates
before patients who coughed a single time, very numerous colonies
of the baccilus were obtained.

But the great advance which has been made rests on the dis¬
covery that bubonic plague is in the vast majority of cases transmitted
by the flea. The pneumonic type forms a very small percentage
of the human cases and even with it, the evidence indicates that the
original infection is derived from a rodent through the intermediary
of the insect.

So modem prophylactic measures are directed primarily against
the rat and fleas. Ships coming from infected ports are no longer
disinfected for the purpose of killing the plague germs, but are fumi¬
gated to destroy the rats and the fleas which they might harbor.
When anchored at infected ports, ships must observe strenuous

174 Arthropods as Direct Inoculators of Disease Germs

precautions to prevent the ingress of rats. Cargo must be inspected
just before being brought on board, in order to insure its freedom from
rats. Even lines and hawsers must be protected by large metal discs
or funnels, for rats readily run along a rope to reach the ship. Once
infested, the ship must be thoroughly fumigated, not only to avoid
carrying the disease to other ports but to obviate an outbreak on
board.

When an epidemic begins, rats must be destroyed by trapping
and poisoning. Various so-called biological poisons have not proved
practicable. Sources of food supply should be cut off by thorough
cleaning up, by use of rat-proof garbage cans and similar measures.
Hand in hand with these, must go the destruction of breeding places,
and the rat-proofing of dwellings, stables, markets, warehouses, docks
and sewers. All these measures are expensive, and a few years ago
would have been thought wholly impossible to put into practice
but now they are being enforced on a large scale in every fight against
the disease.

Rats and other rodents are regularly caught in the danger zone
and examined for evidence of infection, for the sequence of the epi¬
zootic and of the human disease is now understood. In London, rats
are regularly trapped and poisoned in the vicinity of the principal
docks, to guard against the introduction of infected animals in ship¬
ping. During the past six years infected rats have been found
yearly, thirteen having been found in 1912. In Seattle, Washington,
seven infected rats were found along the water front in October, 1913,
and infected ground squirrels are still being found in connection with
the anti-plague measures in California,

The procedure during an outbreak of the human plague was well
illustrated by the fight in San Francisco. The city was districted,
and captured rats, after being dipped in some fluid to destroy the fleas,
were carefully tagged to indicate their source, and were sent to the
laboratory for examination. If an infected rat was found, the officers
in charge of the work in the district involved were immediately
notified by telephone, and the infected building was subjected to a
thorough fumigation. In addition, special attention was given to
all the territory in the four contiguous blocks.

By measures such as these, this dread scourge of the human race
is being brought under control. Incidentally, the enormous losses
due to the direct ravages of rats are being obviated and this alone
would justify the expenditure many times over of the money and
labor involved in the anti-rat measures.

CHAPTER VII

ARTHROPODS AS ESSENTIAL HOSTS OF PATHOGENIC ORGANISMS

We now have to consider the cases in which the arthropod acts
as the essential host of a pathogenic organism. In other words,
cases in which the organism, instead of being passively carried or
merely accidentally inoculated by the bite of its carrier, or vector , is
taken up and undergoes an essential part of its development within
the arthropod.

In some cases, the sexual cycle of the parasite is undergone in the
arthropod, which then serves as the definitive or
primary host. In other cases, it is the asexual stage
of the parasite which is undergone, and the arthropod
then acts as the intermediate host. This distinction
is often overlooked and all the cases incorrectly
referred to as those in which the insect or other
arthropod acts as intermediate host.

We have already emphasized that this is the most
important way in which insects may transmit disease,
for without them the particular organisms concerned
could never complete their development. Exter¬
minate the arthropod host and the life cycle of the
parasite is broken, the disease is exterminated.

As the phenomenon of alternation of generations,
as exhibited by many of the parasitic protozoa, is a
complicated one and usually new to the student, we
shall first take up some of the grosser cases illustrated

113. Dipylidium . . . . .

caninum. The by certain parasitic worms. There is the additional

double pored

tapeworm of the reason that these were the first cases known of arthro-

dog. . . . .

pod transmission of pathogenic organisms.

Insects as Intermediate Hosts of Tapeworms

A number of tapev r orms are known to undergo their sexual stage
in an insect or other arthropod. Of these at least tv r o are occasional
parasites of man.

Dipylidium caninum (figs. 113 and 114), more generally knovm as
Taenia cucumerina or T. elliptica, is the commonest intestinal parasite
of pet dogs and cats. It is occasionally found as a human parasite,
70 per cent of the cases reported being in young children.

175

176 Arthropods as Essential Hosts of Pathogenic Organisms

114. Dipylidium caninum.
Rostrum evaginated and
invaginated. After
Blanchard.

In 1869, Melnikoff found in a dog louse, Trichodectes canis, some
peculiar bodies which Leuckart identified as the larval form of this
tapeworm. The worm is, however, much more
common in dogs and cats than is the skin para¬
site, and hence it appears that the Trichodectes
could not be the only intermediate host. In
1888, Grassi found that it could also develop
in the cat and dog fleas, Ctenocephalus felis
and C. canis , and in the human flea, Pulex
irritans.

The eggs, scattered among the hairs of the
dog or cat, are ingested by the insect host and
in its body cavity they develop into pyriform
bodies, about 300(4. in length, almost entirely destitute of a bladder,
but in the immature stage provided with a caudal appendage (fig. 115).
Within the pear-shaped body (fig. 116) are the invaginated head and
suckers of the future tapeworm. This larval
form is known as a cysticercoid, in contradis¬
tinction to the bladder-like cysticercus of many
other cestodes. It is often referred to in liter¬
ature as Cryptocystis trichodectis Villot.

As many as fifty of the cysticercoids have
been found in the body cavity of a single flea.

When the dog takes up an infested flea or louse,
by biting itself, or when the cat licks them up, the
larvae quickly develop into tapeworms, reaching sexual maturity in
about twenty days in the intestine of their host. Puppies and
kittens are quickly infested when suckling a flea-infested mother, the
developing worms having been found in the intestines of puppies not
more than five or six days old.

Infestation of human beings occurs only
through accidental ingestion of an infested flea.
It is natural that such cases should occur largely
in children, where they may come about in
some such way as illustrated in the accompany¬
ing figures 117 and 118.

Hymenolepis diminuta, very commonly living in the intestine
of mice and rats, is also known to occur in man. Its cysticercoid
develops in the body cavity of a surprising range of meal-infesting
insects. Grassi and Rovelli (abstract in Ransom, 1904) found it in the

115. Dipylidium caninum.
Immature cysticercoid.
After Grassi and Rovelli.

110 .

Dipylidium caninum.
Cysticercoid. After
Villet.

Insects as Intermediate Hosts of Tapeworms

177

larvae and adult of a moth, Asopia farinalis, m the earwig, Anisolabis
annulipes, the Tenebrionid beetles Akis spinosa and Scaurus striatus.

117. One way in which Dipylidium infection in
children may occur. After Blanchard.

Grassi considers that the lepi-
dopter is the normal inter¬
mediate host. The insect takes
up the eggs scattered by rats
and mice. It has been experi¬
mentally demonstrated that
man may develop the tape¬
worm by swallowing infested
insects. Natural infection
probably occurs by ingesting
such insects with cereals, or

imperfectly cooked foods.

Hymenolepis lanceolata, a parasite of geese and ducks, has been
reported once for man. The supposed cysticercoid occurs in various
small crustaceans of the family Cyelopidae.

118 . The probable method by which Dipylidium infection usually occurs.

178 Arthropods as Essential Hosts of Pathogenic Organisms

Several other cestode parasites of domestic animals are believed
to develop their intermediate stage in certain arthropods. Among
these may be mentioned:

Choanotcenia infundibulformis,oi chickens, developing in the house¬
fly (Grassi and Rovelli);

Davainea cesticilhis, of chickens, in some lepidopter or coleopter
(Grassi and Rovelli);

Hymenolepis anatina, H. gracilis, H. sinuosa, H. coronula and
Fimbriaria fasciolaris, all occurring in ducks, have been reported as
developing in small aquatic crustaceans. In these cases, cysticer-
coids have been found which, on account of superficial characters,
have been regarded as belonging to the several species, but direct
experimental evidence is scant.

Arthropods as Intermediate Hosts of Nematode Worms

Filariasis and Mosquitoes— A number of species of Nematode
worms belonging to the genus Filaria, infest man and other verte¬
brates and in the larval condition are to be found in the blood.
Such infestation is known as filariasis. The sexually mature worms
are to be found in the blood, the lymphatics, the mesentery and sub¬
cutaneous connective tissue. In the cases best studied it has been
found that the larval forms are taken up by mosquitoes and undergo
a transformation before they can attain maturity in man.

The larva; circulating in the blood are conveniently designated
as microfilariae. In this stage they are harmless and only one species,
Filaria bancrofti, appears to be of any great pathological significance
at any stage.

Filaria bancrofti in its adult state, lives in the lymphatics of man.
Though often causing no injury it has been clearly established that
they and their eggs may cause various disorders due to stoppage
of the lymphatic trunks (fig. 119). Manson lists among other effects,
abscess, varicose groin glands, lymph scrotum, chyluria, and ele¬
phantiasis.

The geographical distribution of this parasite is usually given as
coextensive with that of elephantiasis, but it is by no means certain
that it is the only cause of this disease and so actual findings of the
parasites arc necessary. Manson reports that it is “an indigenous
parasite in almost every country throughout the tropical and sub¬
tropical world, as far north as Spain in Europe and Charlestown in

Filariasis and Mosquitoes

179

the United States, and as far south as Brisbane in Australia.” In
some sections, fully 50 per cent of the natives are infested. Labredo
(1910) found 17.82 per cent infestation in Havana.

The larval forms of Filaria bancrofti were first discovered in 1863,
by Demarquay, in a case of chylous dropsy. They were subse¬
quently noted under similar conditions, by several workers, and by
Wiicherer in the urine of twenty-eight cases of tropical chyluria,
but in 1872 Lewis found that the blood of man was the normal
habitat, and gave them the name Filaria sanguinis hominis. The

adult worm was found in 1876
by Bancroft, and in 1877,
Cobboldgave it the name Filaria
bancrofti. It has since been
found repeatedly in various parts
of the lymphatic system, and its
life-history has been the subject
of detailed studies by Manson
(1884), Bancroft (1899), Low
(1900), Grassi and Noe (1900),
Noe (1901) and Fullebom (1910).

The larvae, as they exist in
the circulating blood, exhibit a
very active wriggling movement,
without material progression.
They may exist in enormous
numbers, as many as five or
six hundred swarming in a
single drop of blood. This is the more surprising when we con¬
sider that they measure about 300;./. x 8(jl, that is, their width is
equal to the diameter of the red blood corpuscle of their host and
their length over thirty-seven times as great.

Their organs are very immature and the structure obscure. When
they have quieted down somewhat in a preparation it may be seen
that at the head end there is a six-lipped and very delicate prepuce,
enclosing a short “fang” which may be suddenly exserted and
retracted. Completely enclosing the larva is a delicate sheath,
which is considerably longer than the worm itself. To enter into
further details of anatomy is beyond the scope of this discussion
and readers interested are referred to the work of Manson and of
Fullebom.

119. Elephantiasis in Man. From “New
Sydenham Society’s Atlas.”

180 Arthropods as Essential Hosts of Pathogenic Organisms

One of the most surprising features of the habits of these larvae
is the periodicity which they exhibit in their occurrence in the peri¬
pheral blood. If a preparation be made during the day time there
may be no evidence whatever of filarial infestation, whereas a prep¬
aration from the same patient taken late in the evening or during
the night may be literally swarming with the parasites. Manson
quotes Mackenzie as having brought out the further interesting
fact that should a “filarial subject be made to sleep during the day
and remain awake at night, the periodicity is reversed; that is to say,
the parasites come into the blood during the day and disappear from
it during the night.” There have been numerous attempts to explain
this peculiar phenomenon of periodicity but in spite of objections
which have been raised, the most plausible remains that of Manson,
who believes that it is an adaptation correlated with the life-habits
of the liberating agent of the parasite, the mosquito.

The next stages in the development of Filaria nocturna occur in
mosquitoes, a fact suggested almost simultaneously by Bancroft
and Manson in 1877, and first demonstrated by the latter very soon
thereafter. The experiments were first carried out with Culex
quinqnefasciatus (= fatigans ) as a host, but it is now known that a
number of species of mosquitoes, both anopheline and culicine, may
serve equally well.

When the blood of an infested individual is sucked up and reaches
the stomach of such a mosquito, the larvas, by very active movements,
escape from their sheaths and within a very few hours actively mi¬
grate to the body cavity of their new host and settle down primarily
in the thoracic muscles. There in the course of sixteen to twenty
days they undergo a metamorphosis of which the more conspicuous
features are the formation of a mouth, an alimentary canal and a
trilobed tail. At the same time there is an enormous increase in
size, the larvae which measured .3 mm. in the blood becoming 1.5 mm.
in length. This developmental period may be somewhat shortened
in some cases and on the other hand may be considerably extended.
The controlling factor seems to be the one of temperature.

The transformed larvae then reenter the body cavity and finally
the majority of them reach the interior of the labium (fig. 120). A
few enter the legs and antennae, and the abdomen, but these are
wanderers which, it is possible, may likewise ultimately reach the
labium, where they await the opportunity to enter their human host.

Filariasis and Mosquitoes

181

It was formerly supposed that when the infested mosquito punc¬
tured the skin of man, the mature larvae were injected into the cir¬
culation. The manner in which this occurred was not obvious, for
when the insect feeds it inserts only the stylets, the labium itself
remaining on the surface of the skin. Fiillebom has cleared up the
question by showing that at this time the filariae escape and, like
the hookworm, actively bore into the skin of their new host.

Once entered, they migrate to the lymphatics and there quickly
become sexually mature. The full grown females measure 85-90 mm.
in length by .24-28 mm. in diameter, while the males are less than

120. Filaria in the muscles and labium of Culex. After Blanchard.

half this size, being about 40 mm. by .1 mm. Fecundation occurs
and the females will be found filled with eggs in various stages of
development, for they are normally viviparous.

Filaria philippinensis is reported by Ashbum and Craig (1907) as
a common blood filaria in the Philippine Islands. As they describe
it, it differs from Filaria bancrofti primarily in that it does not exhibit
periodicity. Its development has been found to occur in Cidex
quinquejasciatus , where it undergoes metamorphosis in about fourteen
or fifteen days. There is doubt as to the species being distinct from
bancrofti.

Several other species occur in man and are thought to be trans¬
ferred by various insects, among which have been mentioned Taba-
nidse and tsetse-flies, but there is no experimental proof in support
of such conjectures.

182 Arthropods as Essential Hosts of Pathogenic Organisms

Filaria immitis is a dangerous parasite of the dog, the adult worm
living in the heart and veins of this animal. It is one of the species
which has been clearly shown to undergo its development in the
mosquito, particularly in Anopheles maculipennis and Aedes calopus
(= Stegomyia). The larval form occurs in the peripheral blood,
especially at night. When taken up by mosquitoes they differ from
Filaria hancrofti in that they undergo their development in the
Malpighian tubules rather than in the thoracic muscles. In
about twelve days they have completed their growth in the tubules,
pierce the distal end, and pass to the labium. This species occurs
primarily in China and Japan, but is also found in Europe and in the
United States. It is an especially favorable species for studying
the transformations in the mosquito.

Filar ice are also commonly found in birds, and in this country
this is the most available source of laboratory material. We have
found them locally (Ithaca, N. Y.) in the blood of
over sixty per cent of all the crows examined, at
any season of the year, and have also found them
in English sparrows.

In the crows, they often occur in enormous
numbers, as many as two thousand having been
found in a single drop of the blood of the most
heavily infested specimen examined. For study, a
small drop of blood should be mounted on a clean
slide and the coverglass rung with vaseline or oil
to prevent evaporation. In this way they can
be kept for hours.

Permanent preparations may be made by
spreading out the blood in a film on a perfectly
clean slide and staining. This is easiest done by touching the fresh
drop of blood with the end of a second slide which is then held at
an angle of about 45 0 to the first slide and drawn over it without
pressure. Allow the smear to dry in the air and stain in the usual
way with hematoxylin.

Other Nematode Parasites of Man and Animals Developing

in Arthropods

Dracunculus medinensis (fig. 121), the so-called guinea-worm, is
a nematode parasite of man which is widely distributed in tropical
Africa, Asia, certain parts of Brazil and is occasionally imported
into North America.

121. Dracunculus
medinensis; female;
mouth; embryo.
After Bastian and
Leuckart.

Other Nematodes Developing in Arthropods

183

122. Cyclops, the
intermediate host of
Dracunculus.

The female worm is excessively long and slender, measuring nearly
three feet in length and not more than one-fifteenth of an inch in
diameter. It is found in the subcutaneous connective tissue and when
mature usually migrates to some part of the leg.

Here it pierces the skin and there is formed a small
superficial ulcer through which the larvae reach the
exterior after bursting the body of the mother.

Fedtschenko (1879) found that when these larvae
reach the water they penetrate the carapace of the
little crustacean, Cyclops (fig. 122). Here they molt
several times and undergo a metamorphosis. Fedts¬
chenko, in Turkestan, found that these stages required
about five weeks, while Manson who confirmed these
general results, found that eight or nine weeks were
required in the cooler climate of Engand.

Infection of the vertebrate host probably occurs through swallow¬
ing infested cyclops in drinking water. Fedtschenko was unable to
demonstrate this experimentally and objection has been raised against
the theory, but Leiper (1907), and Strassen (1907) succeeded in infest¬
ing monkeys by feeding them on cyclops containing the larvae.

Habronema muscce is a worm which has long been known in its
larval stage, as a parasite of the house-fly. Carter found them in
33 per cent of the house-flies examined in Bombay during July, i860,
and since that time they have been shown to be very widely distrib¬
uted. Italian workers reported them in 12 per cent to 30 per cent
of the flies examined. Hewitt reported finding it rarely in England.
In this country it was first reported by Leidy who found it in about
20 per cent of the flies examined at Philadelphia, Pa. Since then it
has been reported by several American workers. We have found it
at Ithaca, N. Y., but have not made sufficient examinations to justify
stating percentage. Ransom (1913) reports it in thirty-nine out of
one hundred and thirty-seven flies, or 28 per cent.

Until very recently the life-history of this parasite was unknown
but the thorough work of Ransom (1911, 1913) has shown clearly
that the adult stage occurs in the stomach of horses. The embryos,
produced by the parent worms in the stomach of the horse, pass
out with the feces and enter the bodies of fly larvae which are develop¬
ing in the manure. In these they reach their final stage of larval
development at about the time the adult flies emerge from the pupal
stage. In the adult fly they are commonly found in the head.

184 Arthropods as Essential Hosts oj Pathogenic Organisms

123. An Echinorhynchid, showing the spinose retractile proboscis.

124. June beetle (Lachnosterna). Larva

frequently in the proboscis, but they occur also in the thorax and
abdomen. Infested flies are accidentally swallowed by horses and
the parasite completes its development to maturity in the stomach of
its definitive host.

Other Nematodes developing in Arthropods 185

Gigantorhynchus hirudinaceus (= Echinorhynchus gigas) is a com¬
mon parasite of the pig and has been reported as occurring in man.
The adult female is 20-35 cm. long and 4-9 mm. in diameter.
It lacks an alimentary canal and is provided with a strongly spined
protractile rostrum, by means of which it attaches to the intestinal
mucosa of its host.

The eggs are scattered with the feces of the host and are taken
up by certain beetle larvae. In Europe the usual intermediate hosts
are the larvae of the cockchafer, Melolontha vulgaris, or of the flower
beetle, Cetonia aurata. Stiles has shown that in the United States
the intermediate host is the larva of the June bug, Lachnosterna
(fig. 124). It is probable that several of the native species serve in
this capacity.

A number of other nematode parasites of birds and mammals
have been reported as developing in arthropods but here, as in the
case of the cestodes, experimental proof is scant. The cases above
cited are the better established and will serve as illustrations.

CHAPTER VIII

ARTHROPODS AS ESSENTIAL HOSTS OF PATHOGENIC
PROTOZOA

Mosquitoes and Malaria

Under the name of malaria is included a group of morbid symp¬
toms formerly supposed to be due to a miasm or bad air, but now
known to be caused by protozoan parasites of the genus Plasmodium ,
which attack the red blood corpuscles. It occurs in paroxysms,
each marked by a chill, followed by high fever and sweating. The
fever is either intermittent or remittent.

There are three principal types of the disease, due to different
species of the parasite. They are:

1. The benign-tertian, caused by Plasmodium vivax, which under¬
goes its schizogony or asexual cycle in the blood in forty-eight hours
or even less. This type of the disease,—characterized by fever
every two days, is the most wide-spread and common.

2. The quartan fever is due to the presence of Plasmodium
malaria, which has an asexual cycle of seventy-two hours, and there¬
fore the fever recurs every three days. This type is more prevalent
in temperate and sub-tropical regions, but appears to be rare every¬
where.

3. The sub-tertian “aestivo-autumnal,” or “pernicious” fever
is caused by Plasmodium falciparum. Schizogony usually occurs
in the internal organs, particularly in the spleen, instead of in the
peripheral circulation, as is the case of the tertian and quartan forms.
The fever produced is of an irregular type and the period of schizogony
has not been definitely determined. It is claimed by some that the
variations are due to different species of malignant parasites.

It is one of the most wide-spread of human diseases, occurring
in almost all parts of the world, except in the polar regions and in
waterless deserts. It is most prevalent in marshy regions.

So commonplace is malaria that it causes little of the dread
inspired by most of the epidemic diseases, and yet, as Ross says,
it is perhaps the most important of human diseases. Figures regard¬
ing its ravages arc astounding. Celli estimated that in Italy it
caused an average annual mortality of fifteen thousand, representing
about two million cases. In India alone, according to Ross (iqio)

Mosquitoes and Malaria

187

“it has been officially estimated to cause a mean annual death-rate
of five per thousand; that is, to kill every year, on the average, one
million one hundred and thirty thousand.” In the United States
it is widespread and though being restricted as the country develops,
it still causes enormous losses. During the year 1911, “in Alabama
alone there were seventy thousand cases and seven hundred and
seventy deaths.” The weakening effects of the disease, the invasion
of other diseases due to the attacks of malaria, are among the very
serious results, but they cannot be estimated.

Not only is there direct effect on man, but the disease has been one
of the greatest factors in retarding the development of certain regions.
Everywhere pioneers have had to face it, and the most fertile regions
have, in many instances been those most fully dominated by it.
Herrick (1903) has presented an interesting study of its effects on
the development of the southern United States and has shown that
some parts, which are among the most fertile in the world, are
rendered practically uninhabitable by the ravages of malaria. How¬
ard (1909) estimates that the annual money loss from the disease
in the United States is not less than $100,000,000.

It was formerly supposed that the disease was due to a miasm,
to a noxious effluvia, or infectious matter rising in the air from
swamps. In other words its cause was, as the name indicated
“mal aria,” and the deep seated fear of night air is based largely on
the belief that this miasm was given off at night. Its production
was thought to be favored by stirring of the soil, dredging operations
and the like.

The idea of some intimate connection between malaria and
mosquitoes is not a new one. According to Manson, Lancisi noted
that in some parts of Italy the peasants for centuries have believed
that malaria is produced by the bite of mosquitoes. Celli states
that one not rarely hears from such peasants the statement that
“In such a place, there is much fever, because it is full of mosquitoes.”
Koch points out that in German East Africa the natives call malaria
and the mosquito by the same name, Mbit. The opinion was not
lacking support from medical men. Celli quotes passages from the
writings of the Italian physician, Lancisi, which indicate that he
favored the view in 1717.

Dr. Josiah Nott is almost universally credited with having sup¬
ported the theory, in 1848, but as we have already pointed out
his work has been misinterpreted. The statements of Beauperthuy,
(1853) were more explicit.

iSS

Arthropods as Hosts of Pathogenic Protozoa

The clearest early presentation of the circumstantial evidence in
favor of the theory of mosquito transmission was that of A. F. A.
King, an American physician, in 1883. He presented a series of
epidemiological data and showed “how they may be explicable by
the supposition that the mosquito is the real source of the disease,
rather than the inhalation or cutaneous absorption of a marsh vapor.”
We may well give the space to summarizing his argument here for
it has been so remarkably substantiated by subsequent work:

1. Malaria, like mosquitoes, affects by preference low and moist
localities, such as swamps, fens, jungles, marshes, etc.

2. Malaria is hardly ever developed at a lower temperature
than 6o° Fahr., and such a temperature is necessary for the develop¬
ment of the mosquito.

3. Mosquitoes, like malaria, may both accumulate in and be
obstructed by forests lying in the course of winds blowing from
malarious localities.

4. By atmospheric currents malaria and mosquitoes are alike
capable of being transported for considerable distances.

5. Malaria may be developed in previously healthy places by
turning up the soil, as in making excavations for the foundation of
houses, tracks for railroads, and beds for canals, because these opera¬
tions afford breeding places for mosquitoes.

6. In proportion as countries, previously malarious, are cleared
up and thickly settled, periodical fevers disappear, because swamps
and pools are drained so that the mosquito cannot readily find a place
suitable to deposit her eggs.

7. Malaria is most dangerous when the sun is down and the
danger of exposure after sunset is greatly increased by the person
exposed sleeping in the night air. Both facts are readily explicable
by the mosquito malaria theory.

8. In malarial districts the use of fire, both indoors and to those
who sleep out, affords a comparative security against malaria, because
of the destruction of mosquitoes.

9. It is claimed that the air of cities in some way renders the
poison innocuous, for, though a malarial disease may be raging out¬
side, it does not penetrate far into the interior. We may easily
conceive that mosquitoes, while invading cities during their nocturnal
pilgrimages will be so far arrested by walls and houses, as well as
attracted by lights in the suburbs, that many of them will in this
way be prevented from penetrating “far into the interior.”

Mosquitoes and Malaria 189

10. Malarial diseases and likewise mosquitoes are most prevalent
toward the latter part of summer and in the autumn.

11. Various writers have maintained that malaria is arrested by-
canvas curtains, gauze veils and mosquito nets and have recom¬
mended the use of mosquito curtains, “through which malaria can
seldom or never pass.” It can hardly be conceived that these
intercept marsh-air but they certainly do protect from mos¬
quitoes.

12. Malaria spares no age, but it affects infants much less
frequently than adults, because young infants are usually carefully
housed and protected from mosquito inoculation.

Correlated with the miasmatic theory was the belief that some
animal or vegetable organism which lived in marshes, produced
malaria, and frequent searches were made for it. Salisbury (1862)
thought this causative organism to be an alga, of the genus Palmella;
others attributed it to certain fungi or bacteria.

In 1880, the French physician, Laveran, working in Algeria,
discovered an amoeboid organism in the blood of malarial patients
and definitely established the parasitic nature of this disease. Pig¬
mented granules had been noted by Meckel as long ago as 1847, in
the spleen and blood of a patient who had died of malaria, and his
observations had been repeatedly verified, but the granules had been
regarded as degeneration products, and the fact that they occurred
in the body of a foreign organism had been overlooked.

Soon after the discovery of the parasites in the blood, Gerhardt
(1884) succeeded in transferring the disease to healthy individuals
by inoculation of malarious blood, and thus proved that it is a true
infection. This was verified by numerous experimenters and it
was found that inoculation with a very minute quantity of the dis¬
eased blood would not only produce malaria but the particular type
of disease.

Laveran traced out the life cycle of the malarial parasite as it
occurs in man. The details as we now know them and as they are
illustrated by the accompanying figure 125, are as follows:

The infecting organism or sporozoite, is introduced into the cir¬
culation, penetrates a red blood corpuscle, and forms the amoeboid
schizont. This lives at the expense of the corpuscle and as it develops
there are deposited in its body scattered black or reddish black
particles. These are generally called melanin granules, but are
much better referred to as ha?mozoin, as they arc not related to

190 Arthropods as Hosts of Pathogenic Protozoa

melanin. The haemozoin is the most conspicuous part of the para¬
site, a feature of advantage in diagnosing from unstained prepara¬
tions.

As the schizont matures, its nucleus breaks up into a number of
daughter nuclei, each with a rounded mass of protoplasm about it,
and finally the corpuscles are broken down and these rounded bodies

125. Life cycle of the malaria parasite. Adapted from Leuckart’s chart,
by Miss Anna Stryke.

are liberated in the plasma as merozoites. These merozoites infect
new corpuscles and thus the asexual cycle is continued. The malarial
paroxysm is coincident with sporulation.

As early as Laveran’s time it was known that under conditions
not yet determined there are to be found in the blood of malarious
patients another phase of the parasite, differing in form according
to the type of the disease. In the pernicious type these appear as
large, crescent-shaped organisms which have commonly been called
“crescents.” We now know that these are sexual forms.

Mosquitoes and Malaria

191

When the parasite became known there immediately arose specu¬
lations as to the way in which it was transferred from man to man.
It was thought by some that in nature it occurred as a free-living
amoeba, and that it gained access to man through being taken up
with impure water. However, numerous attempts to infect healthy
persons by having them drink or inhale marsh water, or by injecting
it into their circulation resulted in failure, and influenced by Leuckart’s
and Melnikoff’s work on Dipylidium, that of Fedtschenko on Dracun-
culus, and more especially by that of Manson on Filaria, search was
made for some insect which might transfer the parasite.

Laveran had early suggested that the role of carrier might be
played by the mosquito, but Manson first clearly formulated the
hyopthesis, and it was largely due to his suggestions that Ross in
India, undertook to solve the problem. With no knowledge of the
form or of the appearance in this stage, or of the species of mosquito
concerned, Ross spent almost two and a half years of the most arduous
w r ork in the search and finally in August, 1897, seventeen years
after the discovery of the parasite in man, he obtained his first
definite clue. In dissecting a “dappled-winged mosquito,” “every
cell was searched and to my intense disappointment nothing what¬
ever was found, until I came to the insect’s stomach. Here, however,
just as I was about to abandon the examination, I saw a very delicate
circular cell, apparently lying amongst the ordinary cells of the organ
and scarcely distinguishable from them. On looking further,
another and another similar object presented itself. I now focused
the lens carefully on one of these, and found that it contained a few
minute granules of some black substance, exactly like the pigment of
the parasite of malaria. I counted altogether twelve of these cells
in the insect.”

Further search showed that “the contents of the mature pigment
cells did not consist of clear fluid but of a multitude of delicate,
thread-like bodies which on the rupture of the parent cell, were poured
into the body cavity of the insect. They were evidently spores.”

With these facts established, confirmation and extension of
Ross’s results quickly followed, from many different sources. We
cannot trace this work in detail but will only point out that much
of the credit is due to the Italian workers, Grassi, Bignami, and
Bastianelli, and to Koch and Daniels.

It had already been found that when fresh blood was mounted and
properly protected against evaporation, a peculiar change occurred

192 Arthropods as Hosts of Pathogenic Protozoa

in these crescents after about half an hour’s time. From certain
of them there were pushed out long whip-like processes which moved
with a very active, lashing movement. The parasite at this stage
is known as the “flagellated body.” Others, differing somewhat in
details of structure, become rounded but do not give off “flagella.”

The American worker, MacCallum (1897), in studying bird
malaria as found in crows, first recognized the true nature of these
bodies. He regarded them as sexual forms and believed that the
so-called flagella played the part of spermatozoa. Thus, the “flagel¬
lated body” is in reality a microgametoblast, producing micro gametes,
or the male sexual element, while the others constitute the macro¬
gametes, or female elements.

It was found that when blood containing these sexual forms was
sucked up by an Anopheline mosquito and taken into its stomach, a
microgamete penetrated and fertilized a macrogamete in a way
analogous to what takes place in the fertilization of the egg in higher
forms. The resultant, mobile organism is known as the migratory
ookinete. In this stage the parasite bores through the epithelial
lining of the “stomach” (mid-intestine) of the mosquito and becomes
encysted under the muscle layers. Here the oocyst, as it is now
known, matures and breaks up into the body cavity and finally
its products come to lie in the salivary glands of the mosquito. Ten
to twelve days are required for these changes, after which the mos¬
quito is infective, capable of introducing the parasite with its saliva,
when feeding upon a healthy person.

Thus the malarial parasite is known to have a double cycle, an
alternation of generations, of which the asexual stage is undergone in
man, the sexual in certain species of mosquitoes. The mosquito is
therefore the definitive host rather than the intermediate, as usually
stated.

The complicated cycle may be made clearer by the diagram of
Miss Stryke (1912) which, by means of a double-headed mosquito
(fig. 126) endeavors to show how infection takes place through the
biting of the human victim, (at A), in whom asexual multiplication
then takes place, and how the sexual stages, taken up at B in the
diagram, arc passed in the body of the mosquito.

The experimental proof that mosquitoes of the Anopheline group
are necessary agents in the transmission of malaria was afforded in
1900 when two English physicians, Drs. Sambon and Low lived for
the three most malarial months in the midst of the Roman Campagna,

Mosquitoes and Malaria

193

a region famous for centuries as a hot-bed of malaria. The two
experimenters moved about freely throughout the day, exposed

126. Life cycle of the malarial parasite. After Miss Anna Stryke.

themselves to rains and all kinds of weather, drank marsh water,
slept exposed to the marsh air, and, in short, did everything which
was supposed to cause malaria, except that they protected them¬
selves thoroughly from mosquito bites, retiring at sunset to a mosquito-

194 Arthropods as Hosts of Pathogenic Protozoa

'proof hut. Though they took no quinine'and all of their neighbors
suffered from malaria, they were absolutely free from the disease.

To complete the proof, mosquitoes which had fed in Rome on
malarious patients were sent to England and allowed to bite two
volunteers, one of them Dr. Manson’s own son, who had not been
otherwise exposed to the disease. Both of these gentlemen con¬
tracted typical cases of malaria and the parasites were to be found in
abundance in their blood.

Since that time there have been many practical demonstrations
of the fact that malaria is transmitted exclusively by the bite of

mosquitoes and that the destruc¬
tion of the mosquitoes means the
elimination of the disease.

We have said that the malarial
parasite is able to undergo its
development only in certain
species of mosquitoes belonging
to the Anopheline group. It is
by no means certain that all of
this group even, are capable of
acting as the definitive host of
the parasites, and much careful
experiment work is still needed
along this line. In the United
States, several species have been
found to be implicated, Anopheles
quadrimaculatus and Anopheles
crucians being the most common. The characteristics of these species
and the distinctions between them and other mosquitoes will be
discussed in Chapter XII.

In antimalarial work it is desirable to distinguish the anopheline
mosquitoes from the culicine species in all stages. The following
tabulation presents the more striking distinctions between the groups
as represented in the United States.

Anopheles Culex, Aedes, etc.

Eggs: Laid singly in small Deposited in clumps in the
numbers upon the surface of the form of a raft (Culex group) or
water. Eggs lie upon their sides deposited singly in the water or
and float by means of lateral on the ground in places which
expansions (fig. 127). may later be submerged.

127. Eggs of Anopheles. After Howard.

Mosquitoes and Malaria

195

Larva: When at rest floats in
a horizontal position beneath the
surface film. No respiratory
tube but instead a flattened
area on the eighth abdominal
segment into which the two
spiracles open (fig. 128).

Adults: Palpi in both sexes
nearly or quite as long as the
proboscis. Proboscis projecting
forward nearly on line with the
axis of the body. When at rest
on a vertical wall the body is
usually held at an angle with the
vertical (fig. 128). Wings fre¬
quently spotted (fig. 130).

When at rest (with few excep¬
tions) floats suspended in an
oblique or vertical position, or
more rarely nearly horizontal,
with the respiratory tube in
contact with the surface film
(fig. .128).

Palpi short in the female, in
the male usually elongate. Pro¬
boscis projects forward at an
angle with the axis of the body.
When at rest on a vertical wall
the body is usually held parallel
or the tip of the abdomen in¬
clined towards the wall (fig. 128).
Wings usually not spotted.

(a) Normal position of the lar¬
vae of Culex and Anopheles in
the water. Culex. left; Ano¬
pheles, middle; Culex pupa,
right hand figure.

These malarial-bearing species are essentially domesticated
mosquitoes. They develop in any accumulation of water which

stands for a week or more.
Ponds, puddles, rain barrels,
horse troughs, cess-pools, cans,
even the foot-prints of ani¬
mals in marshy ground may
afford them breeding places.
It is clear from what has been said regarding the life cycle of the
malarial parasite that the mosquito is harmless if not itself diseased.
Hence malarial-bearing species may abound in the
neighborhood where there is no malaria, the disease
being absent simply because the mosquitoes are unin¬
fected. Such a locality is potentially malarious and
needs only the introduction of a malarial patient who is
exposed to the mosquitoes. It is found that such patients
may harbor the parasites in their blood long after they
are apparently well and thus may serve as a menace,
just as do the so-called typhoid carriers. In some
malarious regions as high as 80-90 per cent of the natives
are such malaria-carriers and must be reckoned with in
antimalaria measures. 128 (6) Norma

Based upon our present day knowledge of the life cycle c°u S i'e x° n a ni

of the malarial parasite the fight against the disease fh n e °waiL S °"

196

Arthropods as Hosts of Pathogenic Protozoa

becomes primarily a problem in economic entomology, — it is a ques¬
tion of insect control, in its broadest interpretation.

The lines of defence and offence
against the disease as outlined by
Boyce (1909) are -

1. Measures to avoid the reser¬
voir (man):

vSegregation.

Screening of patients.

2. Measures to avoid Anopheles:
Choice of suitable locality,

when possible.

Screening of houses and
porches.

Sleeping under mosquito nets.

3. Measures to exterminate the
Anopheles:

Use of natural enemies.

Use of culirides, oiling ponds,
etc.

Drainage and scavenging to
destroy breeding places.
Enforcement of penalties for
harboring larvae or keeping

129. Larva of Anopheles. After Howard. Stagnant Water.

Educational methods.

4. Systematic treatment with quinine to exterminate theparasites.

Mosquitoes and Yellow Fever

Yellow fever was until recently one of the most dreaded of epi¬
demic diseases. It is an acute, specific and infectious disease, non-
contagious in character but occurring in epidemics, or endemics,
within a peculiarly limited geographical area. It is highly fatal,
but those who recover are generally immune from subsequent at¬
tacks.

It is generally regarded as an American disease, having been
found by Cortez, in Mexico, and being confined principally to the
American continents and islands. It also occurs in Africa and at¬
tempts have been made to show that it was originally an African
disease but there is not sufficient evidence to establish this view.

Mosquitoes and Yellow Fever

197

There have been many noted outbreaks in the United States.
Boston suffered from it in 1691 and again in 1693; New York in
1668 and as late as 1856; Baltimore in 1819. In 1793 occurred the
great epidemic in Philadelphia, with a death rate of one in ten of the
population. In the past century it was present almost every year in
some locality of our Southern States, New Orleans being the greatest
sufferer. In the latter city there were 7848 deaths from the disease
in 1853, 4854 in 1858, and 4046 in 1878. The last notable outbreak

130. Anopheles quadrimaculatus, male and female, (x3>p. After Howard.

was in 1905. Reed and Carroll (1901) estimated that during the
period from 1793 to 1900 there had not been less than 500,000 cases
in the United States.

As in the case of the plague, the most stringent methods of con¬
trol proved ineffective and helplessness, almost hopelessness marked
the great epidemics. A vivid picture of conditions is that given by
Mathew Cary, 1793 (quoted by Kelly, 1906) in “A Short Account of
the Malignant Fever Lately Prevalent in Philadelphia.”

The consternation of the people of Philadelphia at this period
was carried beyond all bounds. Dismay and affright were visible

198 Arthropods as Hosts of Pathogenic Protozoa

in the countenance of almost every person. Of those who remained,
many shut themselves in their houses and were afraid to walk the
streets. * * * The corpses of the most respectable citizens,

even those who did not die of the epidemic, were carried to the grave
on the shafts of a chair (chaise), the horse driven by a negro, un¬
attended by friends or relative, and without any sort of ceremony.

People hastily shifted their course at the sight of a hearse coming
toward them. Many never walked on the footpath, but went into
the middle of the streets to avoid being infected by passing by houses
wherein people had died. Acquaintances and friends avoided each
other in the streets and only signified their regard by a cold nod.
The old custom of shaking hands fell into such disuse that many
shrunk back with affright at even the offer of the hand. A person

Mosquitoes and Yellow Fever

199

with a crape, or any appearance of mourning was shunned 1 ke a
viper. And many valued themselves highly on the skill and address
with which they got to the windward of every person they met.
Indeed, it is not probable that London, at the last stage of the plague,
exhibited stronger marks of terror than were to be seen in Phila-

132. Anopheles crucians. Female (X 4 ). After Howard.

delphia from the 24th or 25th of August until pretty late in Septem¬
ber.”

Such was the condition in Philadelphia in 1793 and, as far as
methods of control of the disease were concerned, there was practi¬
cally no advance during the last century. The dominant theory
was that yellow fever was spread by foniites, that is, exposed bedding,
clothing, baggage, and the like. As late as 1898 a bulletin of the
United States Marine Hospital Service stated:

200

Arthropods as Hosts of Pathogenic Protozoa

“While yellow fever is a communicable disease, it is not con¬
tagious in the ordinary acceptance of the term, but is spread by the
infection of places and articles of bedding, clothing, and furniture.”

Based upon this theory, houses, baggage, freight, even mail,
were disinfected, and the most rigid quarantine regulations were
enforced. The hardships to which people of the stricken regions
were subjected and the financial losses are incalculable. And withal,
the only efficient check upon the disease seemed to be the heavy frosts.

/ \

133. Culex sollicitans. Female (X 4 ). After Howard.

It was found that for some reason, the epidemic abated with cold
weather,—a measure beyond human control.

It is not strange that among the multitude of theories advanced to
explain the cause and method of dissemination of the disease there
should be suggestions that yellow fever was transmitted by the
mosquito. We have seen that Beauperthuy (1855) clearly urged
this theory.

More detailed, and of the greatest influence in the final solution
of the problem were the arguments of Dr. Carlos Finlay, of Havana.
In 1881, in a paper presented before the “Rea Academia de Cicncias
M^dicas, Fisicis y Naturales dc la Habana,” he said:

Mosquitoes and Yellow Fever

201

‘ ‘ I feel convinced that any theory which attributes the origin and
the propagation of yellow fever to atmospheric influences, to mias¬
matic or meteorological conditions, to filth, or to the neglect of general
hygienic precautions, must be considered as utterly indefensible.”

He postulated the existence of a material transportable substance
causing yellow fever,—“something tangible which requires to be
conveyed from the sick to the healthy before the disease can be
propagated” and after discussing the peculiarities of the spread of
the disease and the influence of meteorological conditions, he decides
that the carriers of the disease must be sought among insects. He
continues:

“On the other hand, the fact of yellow fever being characterized
both clinically and (according to recent findings) histologically, by
lesions of the blood vessels and by alterations of the physical and
chemical conditions of the blood, suggested that the insect which
should convey the infectious particles from the patient to the healthy
should be looked for among those which drive their sting into blood
vessels in order to suck human blood. Finally, by reason of other
considerations which need not be stated here, I came to think that
the mosquito might be the transmitter of yellow fever.”

“Assimilating the disease to small-pox and to vaccination, it
occurred to me that in order to inoculate yellow fever it would be
necessary to pick out the inoeulable material from within the blood
vessels of a yellow fever patient and to carry it likewise into the
interior of a blood vessel of a person who was to be inoculated. All
of which conditions the mosquito satisfies most admirably through
its bite.”

In the course of his study of the problem, Finlay made detailed
studies of the life history and habits of the common mosquitoes at
Havana, and arrived at the conclusion that the carrier of the yellow
fever was the Culex mosquito or A 'edes calopus, as it is now known.
With this species he undertook direct experimental tests, and be¬
lieved that he succeeded in transmitting the disease by the bite of
infected mosquitoes in three cases. Unfortunately, possibility
of other exposure was not absolutely excluded, and the experiments
attracted little attention.

Throughout the next twenty years Finlay continued his work on
yellow fever, modifying his original theory somewhat as time went on.
Among his later suggestions was that in the light of Smith’s work
on Texas fever, his theory must be “somewhat modified so as to

202

Arthropods as Hosts of Pathogenic Protozoa

include the important circumstance that the faculty of transmitting
the yellow fever germ need not be limited to the parent insect,
directly contaminated by stinging a yellow fever patient (or per¬
haps by contact with or feeding from his discharges), but may be
likewise inherited by the next generation of mosquitoes issued from
the contaminated parent.” He believed that the bite of a single
mosquito produced a light attack of the disease and was thus effec¬
tive in immunizing the patient. Throughout the period, many
apparently successful attempts to transmit the disease by mosqui¬
toes were made. In the light of present day knowledge we must
regard these as defective not only because possibility of other infec¬
tion was not absolutely excluded but because no account was taken
of the incubation period within the body of the mosquito.

In 1900, while the American army was stationed in Cuba there
occurred an epidemic of yellow fever and an army medical board was
appointed for‘‘the purpose of pursuing scientific investigations with
reference to the acute infectious diseases prevalent on the island.”
This was headed by Walter Reed and associated with him were James
Carroll, Jesse W. Lazear and Aristides Agramonte, the latter a Cuban
immune. For a detailed summary of this work the lay reader can¬
not do better than read Dr. Kelly’s fascinating biography ‘‘Walter
Reed and Yellow Fever.”

Arriving at the army barracks near Havana the Commission first
took up the study of Bacillus icteroides, the organism which Sanarelli,
an Italian physician, had declared the causative agent in yellow fever.
They were unable to isolate this bacillus either from the blood during
life or from the blood and organs of cadavers and therefore turned
their attention to Finlay’s theory of the propagation of yellow fever
by means of the mosquito. In this work they had the unselfish
and enthusiastic support of Dr. Finlay himself, who not only consulted
with them and placed his publications at their disposal, but furnished
eggs from which their experimental mosquitoes were obtained.
Inoculations of eleven non-immunes through the bite of infected
mosquitoes were made, and of these, two gave positive results. The
first of the two was Dr. Carroll who allowed himself to be bitten
by a mosquito which had been caused to feed upon four cases of
yellow fever, two of them severe and two mild. The first patient
had been bitten twelve days before.

Three days after being bitten, Dr. Carroll came down with a
typical case of yellow fever. So severe was the attack that for three

Mosquitoes and Yellow Fever

203

days his life hung in the balance. During his convalescence an
incident occurred which showed how the theory of mosquito trans¬
mission of the disease was generally regarded. We quote from Dr.
Kelly: “One of his nurses who came from Tennessee had had con¬
siderable experience with yellow fever, having indeed, lost her hus¬
band and several children from it. One day early in his illness Dr.
Carroll mentioned to her that he had contracted the disease through
the bite of a mosquito, and noticed that she looked surprised. Some
time later, when well enough to look over the daily records of his
condition, he found this entry: ‘Says he got his illness through the
bite of a mosquito,—delirious’.”

The second case was that of an American who was bitten by four
mosquitoes, two of which had bitten severe (fatal) cases of yellow
fever twelve days previously, one of which had bitten a severe case
(second day) sixteen days before and one which had bitten a severe
case eight days before. Five days later, the subject developed a well
pronounced but mild case of the disease.

In the meantime, another member of the Commission, Dr. Lazear,
was accidentally bitten by a mosquito while collecting blood from
yellow fever patients. Five days later he contracted a typical case
which resulted fatally.

So clear was the evidence from these preliminary experiments
that the commission felt warranted in announcing, October 27, 1900,
that, “The mosquito serves as the intermediate host for the parasite
of yellow fever, and it is highly probable that the disease is only
propagated through the bite of this insect.”

In order to extend the experimental evidence under conditions
which could leave no possibility of infection from other sources, a
special experimental sanitary station, named in honor of the deceased
member of the Commission, was established in an open field near
the town of Quemados, Cuba. Here there were constructed two small
buildings known respectively as the “infected clothing building”
and the “infected mosquito building.”

The infected clothing building, 14 x 20 feet in size, was purposely
so constructed as to exclude anything like efficient ventilation, but
was thoroughly screened to prevent the entrance of mosquitoes.
Into this building were brought sheets, pillow-slips, blankets, etc.,
contaminated by contact with cases of yellow fever and their dis¬
charges, — many of them purposely soiled with a liberal quantity of
black vomit, urine, and fecal matter from patients sick with yellow

204 Arthropods as Hosts of Pathogentc Protozoa

fever. Nothing could better serve as the fomites which were sup¬
posed to convey the dread disease.

Three non-immunes unpacked these articles, giving each a
thorough handling and shaking in order to disseminate through the
air of the room the specific agent of the disease. They were then
used in making up the beds which the volunteers occupied each night
for a period of twenty days. The experiment was repeated three
times, volunteers even sleeping in the soiled garments of yellow fever
victims but in not a single case was there the slightest symptom of
disease. The theory of the spread of yellow fever by fomites was
completely demolished.

The infected mosquito building, equal in size to its companion,
was the antithesis as far as other features were concerned. It was
so constructed as to give the best possible ventilation, and bedding
which was brought into it was thoroughly sterilized. Like the
infected clothing building it was carefully screened, but in this case
it was in order to keep mosquitoes in it as well as to prevent entrance
of others. Through the middle of the room ran a mosquito-proof
screen.

On December 5, 1900, a non-immune volunteer who had been in
the quarantine camp for fifteen days and had had no other possible
exposure, allowed himself to be bitten by five mosquitoes which had
fed on yellow fever patients fifteen or more days previously. The
results were fully confirmatory of the earlier experiments of the
Commission-—at the end of three days, nine and a half hours, the
subject came down with a well marked case of yellow fever.

In all, ten cases of experimental yellow fever, caused by the bite
of infected mosquitoes were developed in Camp Lazear. Through¬
out the period of the disease, other non-immunes slept in the little
building, separated from the patient only by the mosquito-proof
screen, but in no circumstances did they suffer any ill effects.

It was found that a yellow fever patient was capable of infecting
mosquitoes only during the first three or four days after coming
down with the disease. Moreover, after the mosquito has bitten
such a patient, a period of at least twelve days must elapse before
the insect is capable of transmitting the disease.

Once the organism has undergone its twelve day development,
the mosquito may remain infective for weeks. In experiments of
the Commission, two of the mosquitoes transmitted the disease to a
volunteer fiftv-seven davs after their contamination. No other

Mosquitoes and Yellow Fever

205

volunteers presenting themselves, one of these mosquitoes died the
sixty-ninth and one the seventy-first day after their original con¬
tamination, without it being determined whether they were still
capable of transmitting the disease.

So carefully carried out was this work and so conclusive were the
results that Dr. Reed w^as justified in writing:

“Six months ago, when we landed on this island, absolutely noth¬
ing was known concerning the propagation and spread of yellow
fever—it was all an unfathomable mystery—but today the curtain
has been drawn—its mode of propagation is established and we know
that a case minus mosquitoes is no more dangerous than one of
chills and fever.’’

The conclusions of the Commission were fully substantiated by
numerous workers, notably Dr. Guiteras of the Havana Board of
Health, who had taken a lively interest in the work and whose
results were made known in 1901, and by the Brazilian and French
Commission at Sao Paulo, Brazil, in 1903.

Throughout the work of the Army Commission and down to the
present time many fruitless efforts have been made to discover the
specific organism of yellow fever. It was clearly established that
the claims of Sanarelli for Bacillus icteroides were without founda¬
tion. It was found, too, that whatever the infective agent might
be it was capable of passing through a Berkefeld filter and thus be¬
longs to the puzzling group of “filterable viruses.” It was further
found that the virus was destroyed by heating up to 55° C for ten
minutes. It is generally believed that the organism is a Protozoan.

The question of the hereditary transmission of the yellow fever
organism within the mosquito w r as left unsettled by the Army Com¬
mission, though, as w r e have seen, it was raised by Finlay. Marchoux
and Simond, of the French Commission devoted much attention to
this phase of the problem and basing their conclusions on one ap¬
parently positive case, they decided that the disease could be trans¬
mitted through the egg of an infected Aedes calopus to the second
generation and thence to man. The conclusion, w r hich is of very
great importance in the control of yellow fever, has not been verified
by other workers.

Once clearly established that yellow fever w T as transmitted solely
by mosquitoes, the question of the characteristics, habits, and geo¬
graphical distribution of the insect parrier became of vital import¬

ance.

206 Arthropods as Hosts of Pathogenic Protozoa

A'cdes calopus, more commonly known as Stegomyia fasciata or
Stegomyia calopus (fig. 134) is a moderate sized, rather strikingly
marked mosquito. The general color is dark-brown or reddish-
brown, but the thorax has a conspicuous broad, silvery-white curved
line on each side, with two parallel median silvery lines. Between

the latter there is a
slender, broken line.
The whole gives a lyre¬
shaped pattern to the
thorax. The abdomen
is dark with silvery-
white basal bands and
silvery white spots on
each side of the ab¬
dominal segments.
Legs black with rings
of pure white at the
base of the segments.

Size of the female
3.3 to 5 mm.; male 3
to 4.5 mm.

It is pre-eminently
a domesticated species,
being found almost
exclusively about the
habitation of man.
“ Its long association
with man is shown by
many of its habits. It
approaches stealthily

134. The yellow fever mosquito (Aedes calopus), (.\7). from behind It re-

After Howard.

treats upon the slight¬
est alarm. The ankles and, when one is sitting at a table or desk,
the underside of the hands and wrists are favorable points of attack.
It attacks silently, whereas other mosquitoes have a piping or hum¬
ming note. The warning sound has doubtless been suppressed in
the evolutionary process of its adaptation to man. It is extremely
wary. It hides whenever it can, concealing itself in garments,
working into the pockets, and under the lapels of coats, and crawl¬
ing up under the clothes to bite the legs. In houses, it will hide

Mosquitoes and Yellow Fever

207

in dark comers, under picture moldings and behind the heads of
old-fashioned bedsteads. It will enter closets and hide in the folds
of garments.”—Howard.

It was claimed by the French Commission, and subsequently
often stated in discussions of the relation of the mosquito to yellow
fever that the mature Aedes calopus will bite only at night. If this
were true it would be of the greatest importance in measures to
avoid the disease. Unfortunately, the claim was illy founded and
numerous workers have clearly established that the exact converse
is more nearly true, this mosquito being pre-eminently a day species,
feeding most actively in early morning,
about sunrise, and late in the afternoon.

On cloudy days it attacks at any time
during the day. Thus there is peril in
the doctrine that infected regions may
be visited with perfect safety during
the daytime and that measures to
avoid the mosquito attack need be
taken only at night.

Dr. Finlay maintained that the
adult, even when stamed, would not
bite when the temperature was below
23 0 C, but subsequent studies have
shown that this statement needs modi¬
fication. The French Commission,
working at Rio de Janeiro, found that Aedes calopus would bite
regularly at temperatures between 22 0 and 25 0 and that the optimum
temperature was between 27 0 and 30° C, but their experiments led
them to believe that it would bite in nature at a temperature as
low as 17 0 C.

The yellow fever mosquito breeds in cisterns, water barrels,
pitchers and in the various water receptacles about the house. In
our own Southern States it very commonly breeds in the above¬
ground cisterns which are in general use. Often the larvae (fig. 135 b)
are found in flower vases, or even in the little cups of water which
are placed under the legs of tables to prevent their being overrun by
ants. They have been repeatedly found breeding in the holy water
font in churches. In short, they breed in any collection of water in
close proximity to the dwellings or gathering places of man.

135a. Aedes calopus. Pupa.
After Howard.

2o8

Arthropods as Hosts of Pathogenic Protozoa

The life cycle under favorable conditions is completed in from
twelve to fifteen days. These figures are of course very dependent
upon the temperature. The Army Commission in Cuba found that
the cycle might be completed in as brief a period as nine and a half
days. Under less favorable conditions it may be greatly lengthened.

The adults are long lived. We have
seen that during the experimental work
in Cuba specimens were kept in cap¬
tivity for sixty-nine and seventy-one
days, respectively, and that they were
proved to retain their infectivity for at
least fifty-seven days. Dr. Guiteras
subsequently kept an infected adult for
one hundred and fifty-four days.

Low temperatures have a very great
effect not only on development, but on
the activity and even life of the adults.
Long before the method of transmission
of yellow fever was discovered it was well
known that the epidemics were brought
to a close by heavy frosts, and it is now
known that this is due to the killing of
the mosquitoes which alone could spread
the disease.

Aedes calopus has a very wide distri¬
bution since, as Howard says, being a
domestic mosquito, having a fairly long
* life in the adult stage, and having the
custom of hiding itself in the most ingen¬
ious ways, it is particularly subject to car¬
riage for long distances on board vessels,
in railway trains, even packed in baggage. In general, its permanent
distribution is from 40 degrees north latitude to 40 degrees south
latitude (Brumpt), in a belt extending around the world. In the
United States it breeds in most of our Southern States.

Thus, as in the case of malaria, there are many places where the
insect earner is abundant but where yellow fever does not occur.
Such, for instance, are Hawaii, Australia and Asia. An outbreak may
occur at any time that a patient suffering from the disease is allowed
to enter and become a source of infection for the mosquitoes. In

1356. Aedes calopus; larva. (x 7 ).
After Howard.

Mosquitoes and Yellow Fever

209

this connection various writers have called attention to the menace
from the Panama Canal. When it is completed, it will allow of
direct passage from regions where yellow fever is endemic and this
will greatly increase the possibility of its introduction into these places
where it is now unknown. The result, with a wholly non-immune
population, would be appalling.

On the other hand, there are places wholly outside of the normal
range of Aedes calopus where the disease has raged. Such are New
York, Boston, and even Philadelphia, which have suffered notable
epidemics. These outbreaks have been due to the introduction of
infected mosquitoes during the heat of summer, when they have not
only conveyed the disease but have found conditions favorable
for their multiplication. Or, uninfected mosquitoes have been thus
accidentally brought in and developed in large numbers, needing
then only the accidental introduction of cases of the disease to start
an epidemic.

Methods of control of various diseases have been revolutionized
by the discovery that they were insect-borne, but in no other case
has the change been as radical or the results as spectacular as in the
case of yellow fever. The “shot-gun quarantine,” the sufferings and
horrors, the hopelessness of fighting absolutely blindly have given
way to an efficient, clear-cut method of control, based upon the knowl¬
edge that the disease is carried from man to man solely by the mosqui¬
to, Aedes calopus. The lines of defense and offense are essentially
as follows:

In the first place, when a case of yellow fever occurs, stringent
precautions must be adopted to prevent the infection of mosquitoes
and the escape of any already infected. This means that the patient
must be removed to a mosquito-proof room, or ward beyond reach of
the insects, and that the infected room must be thoroughly fumi¬
gated at once, to kill the mosquitoes hiding within it. All cracks
and openings should be closed with strips of paper and fumigation
with burning sulphur or pyrethrum carefully carried out.

It should be remembered that if the first case noted is that of a
resident rather than imported, it means that the mosquito carriers
became infected more than two weeks before the case was diagnosed,
for as we have seen, the germ must undergo a twelve-day period of
development within its insect host. Therefore a careful search must
be made for mild cases which, though unrecognized, may serve as
foci for the spread of the disease.

210

Arthropods as Hosts of Pathogenic Protozoa

In face of a threatened epidemic one of the most essential measures
is to educate the citizens and to gain their complete cooperation in
the fight along modem lines. This may be done through the schools,
the pulpit, places of amusement, newspapers and even bulletin
boards.

Emphasis should be placed on the necessity of both non-immunes
and immunes using mosquito curtains, and in all possible ways
avoiding exposure to the mosquitoes.

Then the backbone of the fight must be the anti-mosquito meas¬
ures. In general, these involve screening and fumigating against
adults, and control of water supply, oiling, and drainage against the
larvae. The region involved must be districted and a thorough survey
undertaken to locate breeding places, which must, if possible,
be eradicated. If they are necessary for water supplies, such as
casks, or cisterns, they should be carefully screened to prevent
access of egg-laying adults.

The practical results of anti-mosquito measures in the fight
against yellow fever are well illustrated by the classic examples of
the work in Havana, immediately following the discoveries of the
Army Commission and by the stamping out of the New Orleans
epidemic in 1905.

The opportunities for an immediate practical application of the
theories of the Army Commission in Havana were ideal. The city
had always been a hotbed of yellow fever and was the principal
source from which the disease was introduced year after year into
our Southern States. It was under martial law and with a military
governor who was himself a physician and thoroughly in sympathy
with the views of the Commission, the rigid enforcement of the
necessary regulations was possible. The story of the first campaign
has been often told, but nowhere more clearly than in Dr. Reed’s
own account, published in the Journal of Hygiene for 1902.

Closer home was the demonstration of the efficacy of these
measures in controlling the yellow fever outbreak in New Orleans
in 1905. During the spring and early summer of the year the disease
had, unperceived, gained a firm foothold in that city and when, in
early July the local Board of Health took cognizance of its existence,
it was estimated that there had been in the neighborhood of one
hundred cases.

Conditions were not as favorable as they had been under martial
law in Havana for carrying on a rigid fight along anti-mosquito lines.

Mosquitoes and Yellow Fever

211

The densely populated city was unprepared, the public had to be
educated, and an efficient organization built up. The local authori¬
ties actively began a general fight against the mosquito but in spite
of their best efforts the disease continued to spread. It was recog¬
nized that more rigid organization was needed and on August 12 th
the United States Public Health and Marine Hospital Sendee was
put in absolute charge of the fight. Up to this time there had been
one hundred and forty-two deaths from a total of nine hundred and
thirteen cases and all of the conditions seemed to threaten an out¬
break to exceed the memorable one of 1878 when, as we have seen
there were four thousand and forty-six deaths.

With the hearty cooperation of the citizens, — physicians and
laymen alike,—the fight was waged and long before frost or any near
approach thereto the disease was stamped out, — a thing unheard of
in previous epidemics. The total loss of life was four hundred and
sixty — about 11 per cent as great as that from the comparable epi¬
demic of 1878. If the disease had been promptly recognized and
combated with the energy which marked the fight later in the sum¬
mer, the outbreak would have made little headway and the great
proportion of these lives would have been saved.

CHAPTER IX

ARTHROPODS AS ESSENTIAL HOSTS OF PATHOGENIC PROTOZOA

Insects and Trypanosomiases

By trypanosomiasis is meant a condition of animal parasitism,
common to man and the lower animals, in which trypanosomes,
peculiar flagellate protozoa, infest the blood. Depending upon the
species, they may be harmless, producing no appreciable ill-effect,
or pathogenic, giving rise to conditions of disease. A number of
these are known to be transferred by insects.

In order that we may
consider more fully the
developmental stage of
these parasites within
their insect host, it is
necessary that we des¬
cribe briefly the structure
of the blood-inhabiting
stage.

The trypanosomes are
elongated, usually point¬
ed, flagellated protozoa
(fig. 136) in which the
single flagellum, bent
under the body, forms the
outer limit of a delicate undulating membrane. It arises near
one end of the organism from a minute centrosome-like body
which is known as the blepheroplast, and at the opposite end extends
for a greater or less distance as a free flagellum. Enclosing, or
close beside the blepheroplast is the small kinetonucleus. The
principal nucleus, round or oval in form, is situated near the center
of the body. Asexual reproductions occurs in this stage, by longi¬
tudinal fission, the nucleus and the blepheroplast dividing independ¬
ently of one another. From the blepheroplast of one of the daughter
cells a new flagellum is formed.

Among the pathogenic species are to be found the causative
organisms of some of the most serious diseases of domestic animals
and even of man. It is probable that these pathogenic species secrete

212

Fleas and Lice as Carriers of Trypanosoma lewisi 213

a specific poison. The majority of them are tropical in distri¬
bution.

Though we are concerned especially with the species which infest
man, we shall first consider two of the trypanosomes of lower animals,
known long before any of those of man had been found.

Fleas and Lice as Carriers of Trypanosoma lewisi .—Trypanosoma
lewisi, the first mammalian trypanosome known, is to be found in the
blood of wild rats. Like its host, it appears to be cosmopolitan in
distribution, having been reported from several localities in the
United States, Brazil, Argentine, England, Germany, France, Italy,
Russia, Asia and Africa.

This species is usually regarded as non-pathogenic, but in experi¬
mental work, especially with white rats, heavy infestations often
result fatally, and naturally infested specimens sometimes show
evidence of injury. Rats which have been infested exhibit at least
temporary immunity against new infection.

Trypanosoma lewisi is transmitted from rat to rat by fleas and
by lice. Rabinowitsch and Kempner (1899) first found that healthy
rats which were kept with infested rats, showed trypanosomes in
their blood after about two weeks. They found the trypanosomes
in the alimentary canal of fleas which had fed on the diseased rats.
On teasing such fleas in physiological salt solution and inoculating
them into fresh rats they were able to produce the infection. Finally,
they showed that the fleas which had fed upon infested rats were
able to carry the parasites to healthy rats. Corresponding experi¬
ments with lice were not successful. Prowazek G9°5) found in the
rat louse ( Hceniatopinus spinulosus ) organisms which he regarded
as developmental stages of the Trypanosoma lewisi. He believed
that the sexual cycle was undergone in this insect.

Nuttall (1908) readily transmitted the trypanosomes through the
agency of fleas, ( Ceratophyllus fasciatus and Ctenopthalmus agyrtes).
He believes that these insects are probably the chief transmitters
of the parasite. He was also able to transmit it from diseased to
healthy rats through the agency of the rat louse. He was unable
to trace any developmental stages in the louse and inclined to the
opinion that Prowazek was deceived by the presence of extraneous
flagellates such as are known to exist in a number of blood-sucking
arthropods.

Nuttall concludes that since three distinct kinds of blood-sucking
insects are capable of transmitting Trypanosoma lewisi it appears

214 Arthropods as Essential Hosts of Pathogenic Protozoa

doubtful that this flagellate is a parasite of the invertebrate “host”
in the sense claimed by Prowazek and other investigators.

Tsetse-flies and Nagana —One of the greatest factors in retarding
the development of certain regions of Africa has been the presence
of a small fly, little larger than the common house-fly. This is the
tsetse-fly, Glossina morsitans (fig. 165) renowned on account of the
supposed virulence of its bite for cattle, horses and other domestic
mammals.

The technical characteristics of the tsetse-flies, or Glossinas, and
their several species, will be found in a later chapter. We need
emphasize only that they are blood-sucking Muscidse and that,
unlike the mosquitoes, the sexes resemble each other closely in struc¬
ture of the mouth-parts, and in feeding habits.

In 1894, Colonel David Bruce discovered that the fly was not in
itself poisonous but that the deadly effect of its bite was due to the
fact that it transmitted a highly pathogenic blood parasite, Trypano¬
soma brucei. This trypanosome Bruce had discovered in the blood
of South African cattle suffering from a highly fatal disease known as
“nagana”. On inoculating the blood of infected cattle into horses
and dogs he produced the disease and found the blood teeming with
the causative organism. In the course of his work he established
beyond question that the “nagana” and the tsetse-fly disease were
identical.

Tsetse-flies of the species Glossina morsitans, which fed upon
diseased animals, were found capable of giving rise to the disease
in healthy animals up 'to forty-eight hours after feeding. Wild
tsetse-flies taken from an infected region to a region where they did
not normally occur were able to transmit the disease to healthy
animals. It was found that many of the wild animals in the tsetse-
fly regions harbored Trypanosoma brucei in their blood, though they
showed no evidence of disease. As in the case of natives of malarial
districts, these animals acted as reservoirs of the parasite. Non-
immune animals subjected to the attacks of the insect earner, quickly
succumbed to the disease.

A question of prime importance is as to whether the insect serves
as an essential host of the pathogenic protozoan or whether it is a
mere mechanical earner. Bruce inclined to the latter view. He was
unable to find living trypanosomes in the intestines or excrements
of the fly or to produce the disease on the many occasions when he

Tsetse-flies and Nagana

215

injected the excrement into healthy animals. Moreover, he had
found that the experimental flies were infective only during the first
forty-eight hours and that if wild flies were taken from the infected
region, “kept without food for three days and then fed on a healthy
dog, they never gave rise to the disease.”

Koch had early described what he regarded as sexual forms from
the intestine of the fly but it remained for Kleine (1909) to experi¬
mentally demonstrate that a part of the life cycle of the parasite
was undergone in the fly. Working with Glossina palpalis, he found
that for a period of ten days or longer after feeding on an animal
suffering from nagana it was non-infective, but that then it became
infective and was able to transmit the disease for weeks thereafter.
He discovered and described developmental stages of the parasite
within the intestine of the insect. In other words, the tsetse-fly
(in nature, Glossina morsitans), serves as an essential host, within
which an important part of the life cycle of the parasite is undergone.
These conclusions were quickly verified by Bruce and numerous
other workers and are no longer open to question. Klein and Taute
are even inclined to think that mechanical transmission plays practi¬
cally no role in nature, unless the fly is interrupted while feeding
and passes immediately to a new animal.

Tsetse-flies and Sleeping Sickness of Man— About the beginning
of the present century a hitherto little known disease of man began
to attract great attention on account of its ravages in Uganda and
the region of Victoria Nyanza in South Africa. It was slow, insidu-
ous and absolutely fatal, characterized in its later stages by dullness,
apathy, and finally absolute lethargy all day long, symptoms which
gave it the name of “sleeping sickness.”

It was soon found that the disease was not a new one but that it
had been known for over a hundred years on the west coast of Africa.
Its introduction into Central and East Africa and its rapid spread
have been attributed primarily to the development of the country,
the formation of new trade routes and the free mingling of native
tribes formerly isolated. It is estimated that in the first ten years
of the present century there were approximately two hundred
thousand deaths from the disease in the Uganda protectorate. In
the British province Bugosa, on the Victoria Nyanza there were
thirty thousand deaths in the period from 1902-1905.

216 Arthropods as Essential Hosts of Pathogenic Protozoa

While the disease is peculiarly African there are a number of
instances of its accidental introduction into temperate regions.
Slaves suffering from it were occasionally brought to America in
the early part of the last century and cases have sometimes been
imported into England. In none of the cases did the disease gain a
foothold or spread at all to other individuals.

In 1902 Dutton described a trypanosome, T. gamhiense, which he
and Forde had found the year before in the blood of a patient suffer¬
ing from a peculair type of fever in Gambia. In 1902-1903 Castel-
lani found the same parasite in the cerebro-spinal fluid of sleeping-
sickness patients and definitely reported it as the causative organism
of the disease. His work soon found abundant confirmation, and
it was discovered that the sleeping sickness was but the ultimate
phase of the fever discovered by Dutton and Forde.

When Castellani made known his discovery- of the trypanosome
of sleeping sickness, Brumpt, in France, and Sambon, in England,
independently advanced the theory that the disease was transmitted
by the tsetse-flv, Glossina palpalis. This theory was based upon the
geographical distribution and epidemiology of the disease. Since
then it has been abundantly verified by experimental evidence.

Fortunately for the elucidation of problems relating to the methods
of transfer of sleeping sickness, Trypanosoma gambiense is patho¬
genic for many species of animals. In monkeys it produces symptoms
very similar to those caused in man. Bruce early showed that
Glossina palpalis “fed on healthy monkeys eight, twelve, twenty-four
and forty-eight hours after having fed on a native suffering from
trypanosomiasis, invariably transmitted the disease. After three
days the flies failed to transmit it.” In his summary in Osier’s
Modem Medicine, he continues “But this is not the only proof that
these flies can carry the infective agent. On the lake shore there
was a large native population among whom we had found about
one-third to be harboring trypanosomes in their blood. The tsetse-
flies caught on this lake shore, brought to the laboratory in cages,
and placed straightway on healthy monkeys, gave them the disease
in every instance, and furnished a startling proof of the danger of
loitering along the lake shore among those infected flies.”

As in the case of nagana, Bruce and most of the earlier investi¬
gators supposed the transmission of the sleeping sickness trypano¬
some by Glossina palpalis to be purely mechanical. The work of
Kleine (1909) clearly showed that for Trypanosoma gambiense as

Tsetse-flies and Sleeping Sickness of Man 217

well as for Trypanosoma brucei the fly served as an essential host.
Indeed, Kleine and many subsequent investigators are inclined to
think that there is practically no mechanical transmission of trypan¬
osomes from animal to animal by Glossina in nature, and that the
many successful experiments of the earlier investigators were due
to the fact that they used wild flies whkh already harbored the
transformed parasite rather than directly inoculated it from the
blood of the diseased experimental animals. While the criticism
is applicable to some of the work, this extreme view is not fully
justified by the evidence at hand.

Kleine states (1912) that Glossina palpalis can no longer be
regarded as the sole transmitter of sleeping sickness. Taute (1911)
had shown that under experimental conditions Glossina morsitans
was capable of transferring the disease and Kleine calls attention to
the fact that in German East Africa, in the district of the Rovuma
River, at least a dozen cases of the disease have occurred recently,
though only Glossina morsitans exists in the district. It appears,
however, that these cases are due to a different parasite, Trypano¬
soma rhodesiense. This species, found especially in north-east
Rhodesia and in Nyassaland, is transferred by Glossina morsitans.
y Other workers maintain that the disease may be transmitted by
various blood-sucking flies, or even bugs and lice which attack man.
Fullebom and Mayer (1907) have shown by conclusive experi¬
ments that Aedes ( Stegomyia ) calopus may transmit it from one
animal to another if the two bites immediately succeed each other.

It is not possible that insects other than the tsetse-flies (and only
certain species of these), play an important role in the transmission
of the disease, else it would be much more wide-spread. Sambon
(1908) pointed out that the hypothesis that is spread by Aedes
calopus is opposed by the fact that the disease never spread in the
Antilles, though frequently imported there by West African slaves.
The same observation would apply also to conditions in our own
Southern States in the early part of the past century.

Since Glossina palpalis acts as an essential host of the parasite
and the chief, if not the only, transmitter, the fight against sleeping
sickness, like that against malaria and yellow fever, becomes pri¬
marily a problem in economic entomology. The minutest detail
of the life-history, biology, and habits of the fly, and of its parasites
and other natural enemies becomes of importance in attempts to
eradicate the disease. Here we can consider only the general features
of the subject.

2i8 Arthropods as Essential Hosts of Pathogenic Protozoa

Glossina palpalis lives in limited areas, where the forest and under¬
growth is dense, along the lake shore or river banks. According to
Hodges, the natural range from shore is under thirty yards, though
the distance to which the flies may follow man greatly exceed this.

It is a day feeder, a fact which may be taken advantage of in
avoiding exposure to its attacks. The young are brought forth alive
and full-grown, one every nine or ten days. Without feeding, they
enter the ground and under favorable conditions, complete their
development in a month or more.

137. Sleeping sickness concentration camp in German East Africa. Report of German
Commission.

Methods of control of the disease must look to the prevention
of infection of the flies, and to their avoidance and destruction.
Along the first line, much was hoped from temporary segregation
of the sick in regions where the fly was not found. On the assump¬
tion that the flies acted as carriers only during the first two or three
days, it was supposed that even the “fly belts” would become safe
within a few days after the sick were removed. The problem was
found to be a much more difficult one when it was learned that after
a given brief period the fly again became infective and remained so
for an indeterminate period. Nevertheless, isolation of the sick
is one of the most important measures in preventing the spread of

South American Trypanosomiasis

219

the disease into new districts. Much, too, is being accomplished
by moving native villages from the fly belts, (c.f. fig. 137.)

All measures to avoid the flies should be adopted. This means
locating and avoiding the fly belts as far as possible, careful screen¬
ing of houses, and protection of the body against bites.

Clearing the jungle along the water courses for some yards beyond
the natural range of the fly has proved a very important measure.
Castellani recommends that the area be one hundred yards and
around a village three hundred yards at least.

Detailed studies of the parasites and the natural enemies of the
tsetse-fly are being undertaken and may ultimately yield valuable
results.

South American Trypanosomiasis — The tsetse-flies are distinc¬
tively African in distribution and until recently there were no tryan-
osomes known to infest man in America. In 1909 Dr. Chagas, of
Rio de Janeiro described a new species, Trypanosoma cruzi, patho¬
genic to man.

Trypanosoma cruzi is the causative organism of a disease common
in some regions of Brazil, where it is known as “opilacao.” It is
especially to be met with in children and is characterized by extreme
anemia, wasting, and stunted development associated with fever,
and enlargenemt of the thyroid glands. The disease is transmitted
by the bites of several species of assassin-bugs, or Reduviidae, not¬
ably by Conorhinus megistus. The evolution of the parasite within
the bug has been studied especially by Chagas and by Brumpt.
From the latter’s text we take the following summary.

The.adult tryanosomes, ingested by a Conorhinus megistus, of
any stage, first change into Crithidia-hke forms and then those
which remain in the stomach become ovoid and non-motile. Brumpt
found these forms in immense numbers, in a Cornohinus which had
been infested fourteen months before. The forms which pass into
the intestine quickly assume the Crithidia form and continue to
develop rapidly under this form. Some weeks later they evolve
into the trypanosome forms, pathogenic for man. They then pass
out with the excrement of the bug and infect the vertebrate host
as soon as they come in contact with any mucous layer (buccal,
ocular or rectal). More rarely they enter through the epidermis.

Brumpt showed that the development could take place in three
species; bed-bugs ( Cimex lectularius, C. hemipterus ) and in the tick

220 Arthropods as Essential Hosts of Pathogenic Protozoa

Ornithodoros moubata. The evolution proceeds in the first two
species of bed-bugs as rapidly as in Conorhinus, or even more rapidly,
but they remain infective for a much shorter time and hence Brumpt
considers that they play a much less important role in the spread of
the disease.

Conorhinus megistus, like related forms in our Southern States,
very commonly frequents houses and attacks man with avidity.
Chagas states that the bites are painless and do not leave any traces.
They are usually inflicted on the lips, or the cheeks and thus the
buccal mucosa of a sleeper may be soiled by the dejections of the
insect and the bite serving as a port of entry of the virus, remain
unnoticed.

The possibility of some of our North American Reduviidse play¬
ing a similar role in the transmission of disease should not be over¬
looked.

Leishmanioses and Insects—Closely related to the trypanosomes
is a group of intracellular parasites which have recently been grouped
by Ross under the genus Leishmania. Five species are known to
affect man. Three of these produce local skin infestations, but two
of them, Leishmania donovani and L. infantum, produce serious and
often fatal systemic diseases.

The first of these, that produced by L. donovani, is an exceedingly
virulent disease common in certain regions of India and China. It
is commonly known as “Kala-azar,” or “dum-dum” fever, and more
technically as tropical leishmaniasis. Patton (1907) believes that
the parasite is transmitted by the bed-bug Cimex hemipterus, and has
described a developmental cycle similar to that which can be found
in artificial cultures. On the other hand, Donovan was unable to
confirm Patton’s w r ork and believes that the true intermediate host is
a Reduviid bug, Conorhinus rubrofasciatus.

Leishmania infantum is the cause of the so-called infantile splenic
leishmaniasis, occurring in northern Africa, Spain, Portugal, Italy,
and possibly other parts of Europe. The parasite occurs habitually
in the dog and is only accidentally transferred to children, Alvares
and da Silva, in Portugal (according to Brumpt, 1913) have found
that the excrement of a flea from a diseased dog contains flagellates,
and they suggest that the infection may be transmitted by the acci¬
dental inoculation of this excrement by means of the proboscis of the
flea, as has been thought to occur in the case of the plague. To this

Leishmanioses and Insects

221

Brumpt objects that they and other workers who thought to trace
the development of Leishmania infantum were apparently misled by
the presence of a harmless Herpetomonas which infests dog fleas in all
countries, even where the leishmaniasis is unknown.

Basile (1910 and 1911) however, carried on numerous experiments
indicating that the disease was transferred from children to dogs
and from dog to dog by the dog flea, and was able to find in the
tissues of the insects forms perfectly identical with those found in
children and in dogs suffering from leishmaniasis. He also found
that Pulex irritans was capable of acting as the carrier.

Of the cutaneous type of leishmaniasis, the best known is the so-
called “Oriental sore,” an ulcerative disease of the skin which is
epidemic in many tropical and subtropical regions. The causative
organism is Leishmania tropica, which occurs in the diseased tissues
as bodies very similar to those found in the spleen in cases of
kala-azar. The disease is readily inoculable and there is no doubt
that it may be transferred from the open sores to abraded surfaces of
a healthy individual by house-flies. It is also believed by a number
of investigators that it may be transferred and directly inoculated
by various blood-sucking insects.

Ticks and Diseases of Man and Animals

We have seen that the way to the discoveries of the relations of
arthropods to disease was pointed out by the work of Leuckart and
Melnikoff on the life cycle of Dipylidium, and of Fedtschenko and
Manson on that of Filaria. They dealt with grosser forms, belonging
to well-recognized parasitic groups.

This was long before the role of any insect as a carrier of patho¬
genic micro-organisms had been established, and before the Protozoa
were generally regarded as of importance in the causation of disease.
The next important step was taken in 1889 when Smith and Kil-
bourrie conclusively showed that the so-called Texas fever of cattle,
in the United States, is due to an intracorpuscular blood parasite
transmitted exclusively by a tick. This discovery, antedating by
eight years the work on the relation of the mosquito to malaria, had a
very great influence on subsequent studies along these lines.

While much of the recent work has dealt with the true insects,
or hexapods, it is now known that several of the most serious diseases
of animals, and at least two important diseases of man are tick
borne. These belong to the types known collectively as babesioses
(or “ piroplasmoses”) , and spirochcetoses.

222 Arthropods as Essential Hosts of Pathogenic Protozoa

The term babesiosis is applied to a disease of man or animals
which is caused by minute protozoan parasites of the genus Babesia,
living in the red blood corpuscles. These parasites have usually been
given the generic name Piroplasma and hence the type of disease
which they cause is often referred to as “ piroplasmosis.” The best
known illustration is the disease known in this country as Texas
fever of cattle.

Cattle Ticks and Texas Fever— The cattle disease, which in the
United States is known as Texas fever, is a widely distributed, exceed¬
ingly acute disease. In Australia it is known as redwater fever and
in Europe as haemoglobinuria, due to the fact that the urine of the
diseased animals is discolored by the breaking down of the red blood
corpuscles infested by the parasite.

In their historical discussion, Smith and Kilbourne, point out that
as far back as 1796 it was noted that Southern cattle, in a state of
apparent health, might spread a fatal disease among Northern herds.
As observations accumulated, it was learned that this infection was
carried only during the warm season of the year and in the depth of
winter Southern cattle were harmless. Moreover, Southern cattle
after remaining for a short time in the North lost their power to
transmit the disease, and the same was true of cattle which had been
driven for a considerable distance.

Very significant was the fact that the infection was not com¬
municated directly from the Southern to Northern cattle but that
the ground over which the former passed was infected by them, and
that the infection was transmitted thence to susceptible cattle after
a period of not less than thirty days had elapsed.

Of course a disease as striking as this, and which caused such
enormous losses of cattle in the region invaded was fruitful in theories
concerning its causation. The most widespread was the belief that
pastures were infected by the saliva, urine, or manure of Southern
cattle. There were not wanting keen observers who suggested that
the disease was caused by ticks, but little weight was given to their
view.

Various workers had described bacteria which they had isolated
from the organs of the diseased animals, but their findings could not
be verified. In 1889, Smith and Kilbourne discovered a minute,
pear-shaped organism (fig. 138) in the red blood corpuscles of a cow
which had succumbed to Texas fever. On account of their shape

Cattle Ticks and Texas Fever

2 23

OOOOO

OOOO®

138.

Babesia bovis in blood corpuscles
After Calli.

they were given the generic name Pyrososma and because they were
usually found two in a corpuscle, the specific name, bigeminum. It

is now generally accepted that
the parasite is the same which
Babes had observed the year
before in Roumanian cattle
suffering from haemoglobinuria,
and should be known as Babesia
bovis (Babes).

By a series of perfectly con¬
clusive experiments carried on
near Washington, D. C., Smith
and Kilboume showed that
this organism was carried from Southern cattle to non-immune ani¬
mals by the so-called Southern cattle
tick, Boophilus annulatus (= Mar-
garopus annulatus) (fig. 139).

Of fourteen head of native cattle
placed in a field with tick-infested
Northern cattle all but two contracted
the disease. This experiment was
repeated with similar results. Four
head of native cattle kept in a plot
with three North Carolina cattle
which had been carefully freed from
ticks remained healthy. A second
experiment the same year gave similar
results.

Still more conclusive was the ex¬
periment showing that fields which a.

had not been entered by Southern
cattle but which had been infected by
mature ticks taken from such animals
would produce Texas fever in native
cattle. On September 13, 1889, sev¬
eral thousand ticks collected from
cattle in North Carolina three and
four days before, were scattered in a
small field near W ashington. Three 139 . Thecattietick(Boophiiusannuiatus).
out of four native animals placed in comftoTk! 61 {b) ma!e ‘ Atter

224 Arthropods as Essential Hosts of Pathogenic Protozoa

this field contracted the disease. The fourth animal was not
examined as to its blood but it showed no external symptoms of
the disease.

In these earlier experiments it was believed that the cattle tick
acted as a carrier of the disease between the Southern cattle and the
soil of the Northern pastimes. “It was believed that the tick ob¬
tained the parasite from the blood of its host and in its dissolution
on the pasture a certain resistant spore form was set free which
produced the disease when taken in with the food.” The feeding of
one animal for some time with grass from the most abundantly

140. Hyalomma aegypticum. After Nuttall and Warburton.

infected field, without any appearance of the disease, made this
hypothesis untenable.

In the experimental work in 1890 the astonishing fact was brought
out that the disease was conveyed neither by infected ticks dis¬
integrating nor by their directly transferring the parasite, but that
it was conveyed by the young hatched from eggs of infected ticks.
In other words, the disease was hereditarily transferred to ticks of
the second generation and they alone were capable of conveying it.

Thus was explained the fact that Texas fever did not appear
immediately along the route of Southern cattle being driven to
Northern markets but that after a certain definite period it mani¬
fested itself. It was conveyed by the progeny of ticks which had
dropped from the Southern cattle and deposited their eggs on the
ground.

Cattle Ticks and Texas Fever

225

These results have been fully confirmed by workers in different
parts of the world,—notably by Koch, in Africa, and by Pound, in
Australia.

The disease is apparently transmitted by Boopliilus annulatus
alone, in the United States, but it, or an almost identical disease,
is conveyed by Ixodes hexagonus in Norway, Ixodes ricinus in Finland
and France and by the three species, Boophilus decoloratus , Hyalomma
cegypticum (fig. 140 and 141), and Hcemaphysalis punctata in Africa.

In spite of the detailed study which it has received, the life cycle
of Babesia bovis has not been satisfactorily worked out. The asexual

reproduction in the
blood of the vertebrate
host has been described
but the cycle in the tick
is practically unknown.

More successful
attempts have been
made to work out the life
cycle of a related species,
Babesia canis, which
causes malignant jaun¬
dice in dogs in Africa
and parts of Southern
Europe. In this in¬
stance, also, the disease
is transmitted by heredity to the ticks of the second generation.
Yet the larval, or “seed ticks,’’ from an infected female are not
capable of conveying the disease, but only the nymphs and adults.
Still more complicated is the condition in the case of Babesia ovis of
sheep, which Motas has shown can be conveyed solely by the adult,
sexually mature ticks of the second generation.

In Babesis canis , Christopher (1907) observed developmental
stages in the tick. He found in the stomach of adult ticks, large
motile club-shaped bodies which he considered as ookinetes. These
bodies pass to the ovaries of the tick and enter the eggs where they
become globular in form and probably represent an oocyst. This
breaks up into a number of sporoblasts which enter the tissues of
the developing tick and give rise to numerous sporozoites, which
collect in the salivary glands and thence are transferred to the
vertebrate host. A number of other species of Babesia are known

141.

Hyalomma aegypticum. Capitulum of female;
(a) dorsal, (6) ventral aspect.

226 Arthropods as Essential Hosts of Pathogenic Protozoa

to infest vertebrates and in all the cases where the method has been
worked out it has been found that the conveyal was by ticks. We
shall not consider the cases more fully here, as we are concerned
especially with the method of transfer of human diseases.

Ticks and Rocky Mountain Spotted Fever of Man — Ever since
1873 there has been known in Montana and Idaho a peculiar febrile
disease of man, which has gained the name of “Rocky Mountain
spotted fever.” Its onset is marked by chills and fever which rapidly
become acute. In about four to seven days there appears a charac¬
teristic eruption on the wrists, ankles or back, which quickly covers
the body.

McClintic (1912) states that the disease has now been reported
from practically all of the Rocky Mountain States, including Arizona,
California, Colorado, Idaho, Montana, Nevada, Oregon, Utah,
Washington, and Wyoming. “Although the disease is far more
prevalent in Montana and Idaho than in any of the other States,
its spread has assumed such proportions in the last decade as to call
for the gravest consideration on the part of both the state and national
health authorities. In fact, the disease has so spread from state
to state that it has undoubtedly become a very serious interstate
problem demanding the institution of measures for its control and
suppression.”

A peculiar feature of the Rocky Mountain spotted fever is a
marked variation in its severity in different localities. In Montana,
and especially in the famous Bitter Root Valley, from 33 per cent to
75 per cent of the cases result fatally. On the other hand, the fatality
does not exceed four per cent in Idaho.

In 1902, Wilson and Chowning reported the causative organism
of spotted fever to be a blood parasite akin to the Babesia of Texas
fever, and made the suggestion that the disease was tick-borne.
The careful studies of Stiles (1905) failed to confirm the supposed
discovery of the organism, and the disease is now generally classed
as due to an invisible virus. On the other hand, the accumulated
evidence has fully substantiated the hypothesis that it is tick-borne.

According to Ricketts (1907) the experimental evidence in sup¬
port of this hypothesis was first afforded by Dr. L. P. McCalla and
Dr. II. A. Brereton, in 1905. These investigators transmitted the
disease from man to man in two experiments. “The tick was
obtained ‘from the chest of a man very ill with spotted fever’ and

Ticks and Rocky Mountain Spotted Fever of Man 227

‘applied to the arm of a man who had been in the hospital for two
months and a half, and had lost both feet from gangrene due to
freezing.’ On the eighth day the patient became very ill and passed
through a mild course of spotted fever, leaving a characteristic
eruption. The experiment was repeated by placing the tick on a
woman’s leg and she likewise was infected with spotted fever.”

The most detailed studies were those of the late Dr. H. T. Ricketts,
and it was he who clearly established the tick hypothesis. In the
summer of 1906 he found that guinea pigs and monkeys are very
susceptible to spotted fever and can readily be infected by inocula¬
tion of blood from patients suffering from the disease. This opened
the way to experimental work on tick transmission. A female tick
was fed upon an infected guinea pig for two days, removed and
isolated for two days and then placed upon a healthy guinea pig.
After an incubation period of three and a half days the experimental
animal contracted a well-marked case of the disease.

A similar result was obtained at the same time by King, and later
in the season Ricketts proved that the male tick was also capable
of transmitting the disease. He found that there was a very inti¬
mate relation of the virus to the tick and that the transmission must
be regarded as biological throughout. Ticks remained infective as
long as they lived and would feed for a period of several months. If
they acquired the disease in the larval or nymphal stage they retained
it during molting and were infective in the subsequent stages. In a
few cases the larvae from an infected female were infective.

The evidence indicated that the tick suffers from a relatively
harmless, generalized infection and the virus proliferates in its
body. The disease probably is transferred through the salivary
secretion of the tick since inoculation experiments show that the
salivary glands of the infected adult contain the virus.

It is probable that in nature the reservoir of the virus of spotted
fever is some one or more of the native small animals. Infected
ticks have been found in nature, and as various wild animals are
susceptible to the disease, it is obvious that it may exist among them
unnoticed. Wilson and Cdowning suggested that the ground squir¬
rel plays the principal role.

Unfortunately, much confusion exists regarding the correct
name of the tick which normally conveys the disease. In the medi¬
cal literature it is usually referred to as Dermacentor occidentalis,
but students of the group now agree that it is specifically distinct.

228 Arthropods as Essential Hosts of Pathogenic Protozoa

Banks has designated it as Dermacentor vennstus and this name is
used in the publications of the Bureau of Entomology. On the other
hand, Stiles maintains that the common tick of the Bitter Root
Valley, and the form which has been collected by the authors who
have worked on Rocky Mountain spotted fever in that region, is
separable from D. venustus, and he has described it under the name of
Dermacentor andersoni.

Maver (1911) has shown experimentally that spotted fever may
be transmitted by several different species of ticks, notably Dermacen¬
tor marginatus , Dermacentor variahilis and Amblyomma americanum.
This being the case, the question of the exact systematic status of
the species experimented upon in the Bitter Root Valley becomes
less important, for since Dermacentor occidentalis, Dermacentor
venustus and Dermacentor andersoni all readily attack man, it is
probable that either species would readily disseminate the disease
if it should spread into their range.

Hunter and Bishop (1911) have emphasized the fact that in the
eastern and southern United States there occur several species which
attack man, and any one of which might transmit the disease from
animal to animal and from animal to man. The following species,
they state, would probably be of principal importance in the Southern
and Eastern States: the lone star tick ( Amblyomma americanum)]
the American dog tick ( Dermacentor variabilis) ; and the gulf-coast
tick ( Amblyomma maculatum). In the extreme southern portions of
Texas, Amblyomma cajennense, is a common pest of man.

Since the evidence all indicates that Rocky Mountain spotted
fever is transmitted solely by the tick, and that some of the wild
animals serve as reservoirs of the virus, it is obvious that personal
prophylaxis consists in avoiding the ticks as fully as possible, and in
quickly removing those which do attack. General measures along
the line of tick eradication must be carried out if the disease is to be
controlled. That such measures are feasible has been shown by the
work which has been done in controlling the tick-borne Texas fever
of cattle, and by such work as has already been done against the
spotted fever tick, which occurs on both wild and domestic animals.
Detailed consideration of these measures is to be found in the
publications of the Public Health and Marine Hospital Service,
and the Bureau of Entomology. Hunter and Bishopp give the
following summarized recommendations for control or eradication
measures in the Bitter Root Valley.

Ticks and Rocky Mountain Spotted Fever of Man 229

(1) A campaign of education, whereby all the residents of the
valley will be made thoroughly familiar with the feasibility of the
plan of eradication, and with what it will mean in the development of
the valley.

(2) The obtaining of legislation to make it possible to dip or oil
all live stock in the Bitter Root Valley.

(3) The obtaining of an accurate census of the horses, cattle,
sheep, mules, and dogs in the valley.

(4) The construction of ten or more dipping vats.

(5) The providing of materials to be used in the dipping mixture.

(6) The organization of a corps of workers to carry on the opera¬
tions.

(7) The systematic dipping of the horses, cattle, sheep, and dogs
of the valley on a definite weekly schedule from approximately March
10 to June 9.

(8) The treatment by hand of the animals in localities remote
from vats, on the same schedule.

They estimate that after three seasons’ operations a very small
annual expenditure would provide against reinfestation of the valley
by the incoming of cattle from other places.

Supplementary measures consist in the killing of wild mammals
which may harbor the tick; systematic burning of the brush and
debris on the mountain side; and in clearing, since the tick is seldom
found on land under cultivation.

CHAPTER X

ARTHROPODS AS ESSENTIAL HOSTS OF PATHOGENIC PROTOZOA

[Continued]

Arthropods and Spiroch.etoses of Man and Animals

The term spiroehaetoses is applied to diseases of man or animals
which are due to protistan parasites belonging to the group of slender,
spiral organisms known as spirochaetes.

There has been much discussion concerning the relationship of
the spirochaetes. Formerly, they were regarded as bacteria closely
related to the forms grouped in the genus Spirillum. The results
of the detailed study which the spirochaetes have received in
recent years, have led most of the workers to consider them as belong¬
ing to the protozoa. The merits of the discussion we are not con¬
cerned with here, but rather with the fact that a number of diseases
caused by spirochaetes are arthropod-borne. The better known of
these we shall discuss.

African Relapsing Fever of Man —It has long been known to the
natives of Africa and to travelers in that country, that the bite of a
certain tick, Ornithodoros moubata, may be followed by severe or
even fatal fever of the relapsing type. Until recent years, it was
supposed that the effect was due to some special virulence of the tick,
just as nagana of cattle was attributed to the direct effect of the bite
of the tsetse-flv. The disease is commonly known as “tick-fever”
or by the various native names of the tick.

In 1904, Ross and Milne, in Uganda, and Dutton and Todd on the
Congo, discovered that the cause of the disease is a spirochsete which
is transmitted by the tick. This organism has been designated by
Novy and Knapp as Spiroclueta duttoni.

Ornithodoros moubata (fig. 142), the carrier of African relapsing
fever, or “tick-fever,” is widely distributed in tropical Africa, and
occurs in great numbers in the huts of natives, in the dust, cracks
and crevices of the dirt floors, or the walls. It feeds voraciously
on man as well as upon birds and mammals. Like others of the
Argasidce, it resembles the bed-bug in its habit of feeding primarily
at night. Dutton and Todd observed that the larval stage is under¬
gone in the egg and that the first free stage is that of the octopod
nymph.

230

African Relapsing Fever of Man

231

142. Ornithodoros moubata. (a) Anterior part of venter; ( b) second stage
nymph; (c) capitulum; ( d) dorsal and ( e) ventral aspect of female;
(/) ventral aspect of nymph; (g) capitulum of nymph. After Nuttall
and Warburton.

232 Arthropods as Essential Hosts of Pathogenic Protozoa

The evidence that the fever is transmitted by this tick is con¬
clusive. Koch found that from five per cent to fifteen per cent, and
in some places, fifty per cent of the ticks captured, harbored the
spirochaete. The disease is readily transmitted to monkeys, rats,
mice and other animals and the earlier experiments along these lines
have been confirmed by many workers.

Not only are the ticks which have fed on infected individuals
capable of conveying the disease to healthy animals but they trans¬
mit the causative organism to their progeny. Thus Mollers (1907),
working in Berlin, repeatedly infected monkeys through the bites
of nymphs which had been bred in the laboratory from infected ticks.
Still more astonishing was his discovery that ticks of the third genera¬
tion were infective. In other words, if the progeny of infected ticks
were fed throughout life on healthy animals, and on maturity de¬
posited eggs, the nymphs which hatched from these eggs would still
be capable of carrying the infection.

The developmental cycle of the spirochaete within the tick has not
been fully worked out, though the general conclusions of Leishman
(1910) have been supported by the recent works of Balfour (1911
and 1912), and Hindle (1912), on the life cycle of spirochaetes affect¬
ing fowls.

Spirochceta duttoni ingested by Ornithodoros moubata apparently
disappear within a few days, but Leishman believed that in reality
they break up into minute granules which are to be found in the
alimentary canal, the salivary glands and the Malpighian tubes of
the tick. These granules, or “coccoid bodies,” as Hindle calls them,
are supposed to be the form in which the spirochaetes infect the new
host. We shall see later that Marchoux and Couvy (1913) dis¬
sent wholly from this interpretation.

According to Leishman, and Hindle, the coccoid bodies are not
injected into the vertebrate host with the saliva of the tick, as are
the sporozoites of malaria with that of the mosquito. Instead, they
pass out with the excrement and secondarily gain access to the
wound inflicted by the tick.

Nuttall (1912) calls attention to the fact that the geographical
distribution of Ornithodoros moubata is far wider than our present
records show for the distribution of the relapsing fever in man and
that there is every reason to fear the extension of the disease. Huts
where the ticks occur should be avoided and it should be remembered
that in infected localities there is special danger in sleeping on the
ground.

European Relapsing Fever

233

European Relapsing Fever —There is widely distributed in Europe
a type of relapsing fever which is caused by Spirochceta recurrentis.
It has long been supposed that this disease is spread by the bed-bug
and there is some experimental evidence to show that it may be
conveyed by these insects.

In 1897, Tictin found that he could infect monkeys by inoculating
the contents of bed-bugs which had fed upon a patient within forty-
eight hours. Nuttall, in 1907, in one experiment succeeded in trans¬
mitting Spirochceta recurrentis from mouse to mouse by bites of bed¬
bugs. The bugs, thirty-five in number, were transferred at short
intervals from one mouse to another, not being allowed to take a
full meal on the first, or infected mouse.

On the other hand, there is much clinical evidence to show that
the European relapsing fever like various other types of the disease
is transmitted from man to man by head and body lice ( Pediculus
humanus and Pediculus corporis).

Interesting supplementary evidence is that of Bayon’s observa¬
tions (1912), in Moscow. ‘ ‘ Having visited the big municipal night hos-
pitals at Moscow I soon noticed that they were kept with such scrupu¬
lous cleanliness, disinfected so lavishly, the beds of iron, the floor cement¬
ed, that it was not possible for bed-bugs to thrive to any extent on
the premises. The people sleeping there were allowed, however,
to sleep in their own clothes. The introduction of these model homes
had not had any effect on the incidence of relapsing fever, for the
places were still hot-beds of the fever during winter. On the other
hand, though I changed my rooms several times, I found bugs in
every successive lodging, and I was told in Moscow, this can hardly
be avoided. Yet no foreigner, or Russian of the better class, ever
catches relapsing fever. To this may be added the fact that when
I asked for clothes-lice and promised to pay a kopec for two, the
attendants from the night hostel brought me next morning a small
ounce bottle crammed with Pediculus capitis (= P. humanus), and
Pediculus vestimentorum (= P. corporis) collected off the sleepers.
If relapsing fever were transmitted by bed-bugs, it would be much
more disseminated than it is at present in Moscow.”

Direct experimental evidence of the agency of lice in transmitting
relapsing fever is especially clear in the case of a type of the disease
prevalent in parts of North Africa. We shall consider this evidence
later.

234 Arthropods as Essential Hosts of Pathogenic Protozoa

Other Types of Relapsing Fever of Man —In addition to the three
types of human relapsing fever already referred to, several others
have been distinguished and have been attributed to distinct species
of spirochastes. The various spirochastoses of man are:

African, caused by 5 . duttoni; European, caused by 5 . recur-
rentis; North African, caused by 5 . berbera; East African, caused
by 5 . rossi; East Indian, caused by 5 . carteri; North American,
caused by 5 . novyi; South American, caused by 5 . duttoni {?)

Nuttall (1912) in his valuable resume of the subject, has em¬
phasized that “in view of the morphological similarity of the sup¬
posedly different species of spirochaetes and their individual variations
in virulence, we may well doubt if any of the ‘species’ are valid.
As I pointed out four years ago, the various specific names given to
the spirochaetes causing relapsing fever in man may be used merely
for convenience to distinguish strains or races of different origin.
They cannot be regarded as valid names, in the sense of scientific
nomenclature, for virulence and immunity reactions are not adequate
tests of specificity.”

North African Relapsing Fever of Man -The type of human
relapsing fever to be met with in Algeria, Tunis, and Tripoli, is due to
a Spirochceta which does not differ morphologically from Spirochceta
duttoni, but which has been separated on biological grounds as
Spirochceta berberi.

Experimenting with this type of disease in Algeria, Sergent and
Foly (1910), twice succeeded in transmitting it from man to monkeys
by inoculation of crushed body lice and in two cases obtained infec¬
tion of human subjects who had received infected lice under their
clothing and who slept under coverings harboring many of the lice
which had fed upon a patient. Their results were negative with
Argas persicus, Cimex lectularius, Musca domestica, Hcematopinus
spinulosus and Ceratophyllus fasciatus. They found body lice
associated with every case of relapsing fever which they found in
Algeria.

Nicolle, Blaizot, and Conscil (1912) showed that the louse did
not transmit the parasite by its bite. Two or three hours after it
has fed on a patient, the spirochaetes begin to break up and finally
they disappear, so that after a day, repeated examinations fail to
reveal them. They persist, nevertheless, in some unknown form,
for if the observations are continued they reappear in eight to twelve

Spirochcetosis of Fowls

235

days. These new forms are virulent, for a monkey was infected
by inoculating a single crushed louse which had fed on infected blood
fifteen days before.

Natural infection is indirect. Those attacked by the insect
scratch, and in this act they excoriate the skin, crush the lice and
contaminate their fingers. The least abrasion of the skin serves for
the entrance of the spirochastes. Even the contact of the soiled
fingers on the various mucosa, such as the conjunctive of the eye,
is sufficient.

As in the ease of Spirocheeta duttoni, the organism is transmitted
hereditarily in the arthropod vector. The progeny of lice which
have fed on infected blood may themselves be infective.

Spirochaetosis of Fowls —One of the best known of the spirochaetes
transmitted by arthropods is Spirocheeta gallinarum, the cause of a
very fatal disease of domestic fowls in widely separated regions of
the world. According to Nuttall, it occurs in Southeastern Europe,
Asia, Africa, South America and Australia.

In 1903, Marchoux and Salimbeni, working in Brazil, made the
first detailed study of the disease, and showed that the causative
organism is transmitted from fowl to fowl by the tick Argas persicus.
They found that the ticks remained infective for at least five months.
Specimens which had fed upon diseased birds in Brazil were sent to
Nuttall and he promptly confirmed the experiments. Since that
date many investigators, notably Balfour and Kindle, have contri¬
buted to the elucidating of the life-cycle of the parasite. Since it
has been worked out more fully than has that of any of the human
spirochaetes, we present Hindle’s diagram (fig. 143) and quote the
brief summary from his preliminary paper (19116).

“Commencing with the ordinary parasite in the blood of the fowl,
the spirochaete grows until it reaches a certain length (16—1991.) and
then divides by transverse division. This process is repeated, and
is probably the only method of multiplication of the parasite within
the blood. When the spirochaetes disappear from the circulation,
some of them break up into the coccoid bodies which, however,
do not usually develop in the fowl. When the spirochaetes are
ingested by Argas persicus, some of them pass through the gut wall
into the coelomic fluid. From this medium they bore their way into
the cells of the various organs of the tick and there break up into a
number of coccoid bodies. These intracellular forms multiply by

236 Arthropods as Essential Hosts of Pathogenic Protozoa

ordinary fission in the cells of the Malpighian tubules and gonads.
Some of the coccoid bodies are formed in the lumen of the gut and
Malpighian tubules. The result is that some of the coccoid bodies
may be present in the Malpighian secretion and excrement of an
infected tick and when mixed with the coxal fluid may gain entry
into another fowl by the open wound caused by the tick’s bite. They

then elongate and redevelop into ordinary spirochastes in the blood
of the fowl, and the cycle may be repeated.

Hindle’s account is clear cut and circumstantial, and is quite in
line with the work of Balfour, and of Leishman. Radically different
is the interpretation of Marchoux and Couvy (1913). These investi¬
gators maintain that the granules localized in the Malpighian tubules
in the larvae and, in the adult, also in the ovules and the genital ducts
of the male and female, are not derivod from spirochaetes but that they
exist normally in many acariens. They interpret the supposed

Typhus Fever and Pediculidce

237

disassoeiation of the spirochsete into granules as simply the first
phase, not of a process of multiplication, but of a degeneration
ending in the death of the parasite. The fragmented chromatin
has lost its affinity for stains, remaining always paler than that of
the normal spirochastes. On the other hand, the granules of Leish-
man stain energetically with all the basic stains.

Further, according to Marchoux and Couvy, infection takes
place without the emission of the coxal fluid and indeed, soiling of the
host by the coxal fluid diluting the excrement is exceptional. All
of the organs of the Argasid are invaded by the parasites, but they
pass from the coelom into the acini of the salivary glands and collect
in its efferent canal. The saliva serves as the vehicle of infection.

Thus, the question of the life cycle of Spirochceta gallinarum , and
of spirochsetes in general, is an open one.

It should be noted that Argas persicus, the carrier of Spirochceta
gallinarum, is a common pest of poultry in the southwestern United
States. Though the disease has not been reported from this counting
conditions are such that if accidentally introduced, it might do great
damage.

Other Spirochaete Diseases of Animals About a score of other
blood inhabiting spirochastes have been reported as occurring in
mammals, but little is known concerning their life-histories. One
of the most important is Spirochceta theileri which produces a spiro-
chastosis of cattle in the Transvaal. Theiler has determined that it
is transmitted by an Ixodid tick, Margaropus decoloratus.

Typhus Fever and Pediculidce

Typhus is an acute, and continued fever, formerly epidemically
prevalent in camps, hospitals, jails, and similar places where persons
were crowded together under insanitary conditions. It is accom¬
panied by a characteristic rash, which gives the disease the common
name of “spotted” or “lenticular” fever. The causative organism
is unknown.

Typhus fever has not generally been supposed to occur in the
United States, but there have been a few outbreaks and sporadic
cases recognized. According to Anderson and Goldberger (1912a),
it has been a subject of speculation among health authorities why,
in spite of the arrival of occasional cases in this country and of many
persons from endemic foci of the disease, typhus fever apparently
does not gain a foothold in the United States. These same workers

238 Arthropods as Essential Hosts of Pathogenic Protozoa

showed that the so-called Brill’s disease, studied especially in New
York City, is identical with the typhus fever of Mexico and of
Europe.

The conditions under which the disease occurs and under which
it spreads most rapidly are such as to suggest that it is carried by
some parasitic insect. On epidemiological grounds the insects most
open to suspicion are the lice, bed-bugs and fleas.

In 1909, Nicolle, Comte and Conseil, succeeded in transmitting
typhus fever from infected to healthy monkeys by means of the
body louse ( Pediculus corporis). Independently of this work,
Anderson and Goldberger had undertaken work along this line in
Mexico, and in 1910 reported two attempts to transmit the disease
to monkeys by means of body lice. The first experiment resulted
negatively, but the second resulted in a slight rise in temperature,
and in view of later results it seems that this was due to infection
with typhus.

Shortly after, Ricketts and Wilder (1910) succeeded in transmitt¬
ing the disease to the monkey by the bite of body lice in two experi¬
ments, the lice in one instance deriving their infection from a man
and in another from the monkey. Another monkey was infected
by typhus through the introduction of the feces and abdominal
contents of infested lice into small incisions. Experiments with
fleas and bed-bugs resulted negatively.

Subsequently, Goldberger and Anderson (19126) indicated that
the head louse ( Pediculus humanus ) as well, may become infected
with typhus. In an attempt to transmit typhus fever (Mexican
virus) from man to monkey by subcutaneous injection of a saline
suspension of crushed head lice, the monkeys developed a typical
febrile reaction with subsequent resistance to an inoculation of
virulent typhus (Mexican) blood. In one of the three experiments
to transmit the disease from man to monkey by means of the bite
of the head louse, the animal bitten by the presumably infected head
lice proved resistant to two successive immunity tests with viru¬
lent typhus blood.

In 1910, Ricketts and Wilder reported an experiment undertaken
with a view to determining whether the young of infected lice were
themselves infected. Young lice were reared to maturity on the
bodies of typhus patients, so that if the eggs were susceptible to
infection at any stage of their development, they would have every
opportunity of being infected within the ovary. The eggs of these
infected lice were obtained, they were incubated, and the young lice

Typhus Fever and Pediculidce

239

of the second generation were placed on a normal rhesus monkey.
The experimenters were unable to keep the monkey under very
close observation during the following three or four weeks, but from
the fact that he proved resistant to a subsequent immunity test
they concluded that he probably owed this immunity to infection
by these lice of the second generation.

Anderson and Goldberger (19126) object that due consideration
was not given to the possibility of a variable susceptibility of the
monkey to typhus. Their similar experiment was “frankly nega¬
tive.”

Prophylaxis against typhus fever is, therefore, primarily a ques¬
tion of vermin extermination. A brief article by Dr. Goldberger
(1914) so clearly shows the practical application of his work and that
of the other investigators of the subject, that we abstract from it
the following account:

“ In general terms it may be stated that association with a case of
typhus fever in the absence of the transmitting insect is no more
dangerous than is association with a case of yellow fever in the
absence of the yellow fever mosquito. Danger threatens only when
the insect appears on the scene.”

“We may say, therefore, that to prevent infection of the indi¬
vidual it is necessary for him only to avoid being bitten by the louse.
In theory this may readily be done, for we know that the body louse
infests and attaches itself almost entirely to the body linen, and that
boiling kills this insect and its eggs. Individual prophylaxis is
based essentially, therefore, on the avoidance of contact with indi¬
viduals likely to harbor lice. Practically, however, this is not
always as easy as it may seem, especially under the conditions of
such intimate association as is imposed by urban life. Particularly
is this the case in places such as some ol the large Mexican cities,
where a large proportion of the population harbors this vermin.
Under such circumstances it is well to avoid crowds or crowded places,
such as public markets, crowded streets, or public assemblies at
which the ‘peon’ gathers.”

“Community prophylaxis efficiently and intelligently carried out
is, from a certain point of view, probably easier and more effective
in protecting the individual than is the individual’s own effort to
guard himself. Typhus emphasizes, perhaps better than any other
disease, the fact that fundamentally, sanitation and health are
economic problems. In proportion as the economic condition of the
masses has improved — that is, in proportion as they could afford

240 Arthropods as Essential Hosts of Pathogenic Protozoa

to keep clean-—the notorious filth disease has decreased or dis¬
appeared. In localities where it still prevails, its further reduction
or complete eradication waits on a further improvement in, or exten¬
sion of, the improved economic status of those afflicted. Economic
evolution is very slow process, and, while doing what we can to hasten
it, we must take such precautions as existing conditions permit,
looking to a reduction in or complete eradication of the disease.”

“When possible, public bath houses and public wash houses,
where the poor may bathe and do their washings at a minimum or
without cost, should be provided. Similar provision should be
made in military and construction camps. Troops in the field should
be given the opportunity as frequently as possible to wash and scald
or boil their body linen.”

“Lodging houses, cheap boarding houses, night shelters, hospitals,
jails and prisons, are important factors in the spread and frequently
constitute foci of the disease. They should receive rigid sanitary
supervision, including the enforcement of measures to free all inmates
of such institutions of lice on admission.”

“So far as individual foci of the disease are concerned these
should be dealt with by segregating and keeping under observation
all exposed individuals for 14 days—the period of incubation—from
the last exposure, by disinfecting (boiling or steaming) the suspected
bedding, body linen, and clothes, for the destruction of any possible
vermin that they may harbor, and by fumigating (with sulphur)
the quarters that they may have occupied.”

“It will be noted that nothing has been said as to the disposition
of the patient. So far as the patient is concerned, he should be
removed to ‘clean’ surroundings, making sure that he does not
take with him any vermin. This may be done by bathing, treating
the hair with an insecticide (coal oil, tincture of larkspur), and a
complete change of body linen. Aside from this, the patient may
be treated or cared for in a general hospital ward or in a private house,
provided the sanitary officer is satisfied that the new surroundings
to which the patient has been removed are ‘clean,’ that is, free
from vermin. Indeed, it is reasonably safe to permit a ‘clean’
patient to remain in his own home if this is ‘clean,’ for, as has al¬
ready been emphasized, there can be no spread in the absence of lice.
This is a common experience in native families of the better class
and of Europeans in Mexico City.”

“Similarly the sulphur fumigation above prescribed may be
dispensed with as unnecessary in this class of cases.”

CHAPTER XI

SOME POSSIBLE, BUT IMPERFECTLY ESTABLISHED CASES OF
ARTHROPOD TRANSMISSION OF DISEASE

Infantile Paralysis or Acute Anterior Poliomyelitis

The disease usually known in this country as infantile paralysis
or, more technically, as acute anterior poliomyelitis, is one which
has aroused much attention in recent years.

The causative organism of infantile paralysis is unknown, but
it has been demonstrated that it belongs to the group of filterable
viruses. It gives rise to a general infection, producing characteristic
lesions in the central nervous system. The result of the injury to
the motor nerves is a more or less complete paralysis of the corres¬
ponding muscle. This usually manifests itself in the legs and arms.
The fatal cases are usually the result of paralysis of the muscles
of respiration. Of the non-fatal cases about 60 per cent remain
permanently crippled in varying degrees.

Though long known, it was not until about 1890 that it was
emphasized that the disease occurs in epidemic form. At this time
Medin reported his observations on an epidemic of forty-three cases
which occurred in and around Stockholm in 1887. Since then,
according to Frost (1911), epidemics have been observed with increas¬
ing frequency in various parts of the world. The largest recorded
epidemics have been those in Vermont, 1894, 126 cases; Norway and
Sweden, 1905, about 1,500 cases; New York City, 1907, about
2,500 cases. Since 1907 many epidemics have been reported in the
United States, and especially in the Northern States east of the
Dakotas. In 1912 there were over 300 cases of the disease in Buffalo,
N. Y., with a mortality of somewhat over 11 per cent.

In view of the sudden prominence and the alarming spread of
infantile paralysis, there have been many attempts to determine
the cause, and the manner in which the disease spreads and develops
in epidemic form. In the course of these studies, the question of
possible transmission by insects was naturally suggested.

C. W. Howard and Clark (1912) presented the results of studies
in this phase of the subject. They dealt especially with the house¬
fly, bedbug, head, and body lice, and mosquitoes. It was found
that the house-fly {Musea domestica) can carry the virus of poliomye¬
litis in an active state for several days upon the surface of the body

241

242 Arthropod Transmission of Disease

and for several hours within the gastro-intestinal tract. Mosquitoes
and lice were found not to take up or maintain the virus. On the
other hand, the bedbug ( Cimex lectularius) was found to take the
virus from the infected monkeys and to maintain it in a living state
within the body for a period of seven days. This was demonstrated
by grinding up in salt solution, insects which had fed on poliomyeletic
animals and injecting the filtrate into a healthy monkey. The experi¬
menters doubted that the bedbug is a carrier of the virus in nature.

Earlier in the same year, Braes and Sheppard published the results
of an intensive epidemiological study of the outbreak of 1911, in
Massachusetts. Special attention had been paid to the possibility
of insect transfer and the following conclusion was reached:

“Field work during the past summer together with a consideration
of the epidemiology of the disease so far as known, points strongly
toward biting flies as possible carriers of the virus. It seems probable
that the common stable-fly ( Stomoxys calcitrans L.) may be responsi¬
ble to a certain extent for the spread of acute epidemic poliomyelitis,
possibly aided by other biting flies, such as Tabanus lineola. No
facts which disprove such a hypothesis have as yet been adduced,
and experiments based upon it are now in progress.”

As stated by Braes (1913), especial suspicion fell upon the stable-
fly because:

1. The blood-sucking habits of the adult fly suit it for the transfer
of virus present in the blood.

2. The seasonal abundance of the fly is very closely correlated
with the incidence of the disease, rising rapidly during the summer
and reaching a maximum in July and August, then slowly declining
in September and October.

3. The geographical distribution of the fly is, so far as can be
ascertained, wider, or at least eo-extensive with that of poliomyelitis.

4. Stomoxys is distinctly more abundant under rural conditions,
than in cities and thickly populated areas.

5. While the disease spreads over districts quickly and in a
rather erratic way, it often appears to follow along lines of travel,
and it is known that Stomoxys flies will often follow horses for long
distances along highways.

6. In a surprisingly large number of cases, it appeared probable
that the children affected had been in the habit of frequenting places
where Stomoxys is particularly abundant, i.e., about stables, barn¬
yards, etc.

Infantile Paralysis or Acute Anterior Poliomyelites 243

The experiments referred to were earned on during the summer of
1912 and in September Dr. Rosenau announced that the disease was
transferred by the bite of the stable-fly.

A monkey infected by inoculation was exposed to the bites of
upwards of a thousand of the Stomoxys flies daily, by stretching it
at full length and rolling it in a piece of chicken wire, and then placing
it on the floor of the cage in which the flies were confined. The flies
fed freely from the first, as well as later, after paralysis had set in.
Alternating with the inoculated monkey, healthy monkeys were
similarly introduced into the cage at intervals. New monkeys were
inoculated to keep a supply of such infected animals and additional
healthy ones were exposed to the flies, which fed willingly and in
considerable numbers on each occasion. “Thus the flies were given
every opportunity to obtain infection from the monkeys, since the
animals were bitten during practically every stage of the disease
from the time of the inoculation of the virus till their death follow¬
ing the appearance of paralysis. By the same arrangement the
healthy monkeys were likely to be bitten by flies that had previously
fed during the various stages of the disease on the infected monkeys.
The flies had meanwhile enjoyed the opportunity of incubating the
virus for periods varying from the day or two which usually elapses
between consecutive feedings, to the two or three-week period for
which at least some (although a very small percentage) of the flies
lived in the cage.”

“In all, twelve apparently healthy monkeys of a small Japan
species were exposed to the flies in the manner described for the in¬
fected monkeys. Some were placed in the cage only once or twice
and others a number of times after varying intervals. These ex¬
posures usually lasted for about half an hour, but were sometimes
more protracted. No results were apparent until two or three
weeks after the experiment was well under way, and then in rather
rapid succession six of the animals developed symptoms of poliomye¬
litis. In three, the disease appeared in a virulent form, resulting
in death, while the other three experienced transient tremblings,
diarrhoea, partial paralysis and recovery.” — Brues, 1913.

Very soon after the announcement of the results of experiments
by Rosenau and Brues, they were apparently conclusively confirmed
by Anderson and Frost (1912), who repeated the experiments, at
Washington. They announced that through the bites of the Stomoxys
flies that had previously fed on infected monkeys, they had succeeded
in experimentally infecting three healthy monkeys.

244

Arthropod Transmission of Disease

The results of these experiments gained much publicity and in
spite of the conservative manner in which they had been announced,
it was widely proclaimed that infantile paralysis was conveyed in
nature by the stable-fly and by it alone.

Serious doubt was cast on this theory by the results of further
experiments by Anderson and Frost, reported in May of 1913.
Contrary to the expectations justified by their first experience, the
results of all the later, and more extended, experiments were wholly
negative. Not once were these investigators again able to transmit
the infection of poliomyelitis through Stomoxys. They concluded that
it was extremely doubtful that the insect was an important factor
in the natural transmission of the disease, not only because of their
series of negative results, “but also because recent experiments have
afforded additional evidence of the direct transmissibility or con¬
tagiousness of poliomyelitis, and because epidemiological studies
appear to us to indicate that the disease is more likely transmitted
largely through passive human virus carriers.”

Soon after this, Kling and Levaditi (1913) published their detailed
studies on acute anterior poliomyelitis. They considered that the
experiments of Flexner and Clark (and Howard and Clark), who fed
house-flies on emulsion of infected spinal cord, were under conditions
so different from what could occur in nature that one could not
draw precise conclusions from them regarding the epidemiology of
the disease. They cited the experiments of Josef son (1912), as
being under more reasonable conditions. He sought to determine
whether the inoculation of monkeys with flies caught in the wards of
the Hospital for Contagious Diseases at Stockholm, where they had
been in contact with cases of poliomyelitis, would produce the
disease. The results were completely negative.

Kling and Lavaditi made four attempts of this kind. The flies
were collected in places where poliomyelitics had dwelt, three, four
and twenty-four after the beginning of the disease in the family and
one, three, and fifteen days after the patient had left the house.
These insects were for the greater part living and had certainly been
in contact with the infected person. In addition, flies were used
which had been caught in the wards of the Hospital for Contagious
Diseases at Soderkoping, when numbers of poliomyelitics were con¬
fined there. Finally, to make the conditions as favorable as possible,
the emulsions prepared from these flies were injected without previous
filtering, since filtration often causes a weakening of the virus. In

Infantile Paralysis or Acute Anterior Poliomyelitis 245

spite of these precautions, all their results were negative, none of the
inoculated animals having contracted poliomyelitis. They also
experimented with bedbugs which had fed upon infected patients at
various stages of the disease, but the results in these cases also were
wholly negative.

Kling and Levaditi considered at length the possibility of trans¬
mission of the disease by Stomoxys. As a result of their epidemiologi¬
cal studies, they found that infantile paralysis continued to spread
in epidemic form in the dead of winter, when these flies were very
rare and torpid, or were even completely absent. Numerous cases
developed in the northern part of Sweden late in October and
November, long after snow had fallen. On account of the rarity
of the Stomoxys flies during the period of their investigations they
v r ere unable to conduct satisfactory" experiments. In one instance,
during a severe epidemic, they found a number of the flies in a stable
near a house inhabited by an infected family, though none w r as
found in the house itself. These flies were used in preparing an
emulsion which, after filtering, was injected into the peritoneal
cavity of a monkey. The result was wholly negative.

As for the earlier experiments, Kling and Levaditi believe if the
flies w r ere responsible for the transmission of the disease in the cases
reported by Rosenau and Brues, and the first experiments of Ander¬
son and Frost, it w r as because the virus of infantile paralysis is elimi¬
nated with the nasal secretions of paralyzed monkeys and the flies,
becoming contaminated, had merely acted as accidental carriers.

Still further evidence against the hypothesis of the transmission
of acute anterior poliomyelitis by Stomoxys calcitrans was brought
forward by Sawyer and Herms (1913). Special precautions were
used to prevent the transference of saliva or other possibly infectious
material from the surface of one monkey to that of another, and to
avoid the possibility of complicating the experiments by intro¬
ducing other pathogenic organisms from wild flies, only laboratory-
bred flies were used. In a series of seven carefully performed experi¬
ments, in which the conditions were varied, Sawryer and Herms were
unable to transmit poliomyelitis from monkey to monkey through
the agency of Stomoxys, or to obtain any indication that the fly is the
usual agent for spreading the disease in nature.

The evidence at hand to date indicates that acute anterior polio¬
myelitis, or infantile paralysis, is transmitted by contact with in¬
fected persons. Under certain conditions insects may be agents in
spreading the disease, but their role is a subordinate one.

246 Arthropod Transmission of Disease

Pellagra

Pellagra is an endemic and epidemic disease characterized by a
peculiar eruption or erythema of the skin (figs 144 and 145), digestive

disturbances and nervous trouble.
Insanity is a common result, rather
than a precursor of the disease.
The manifestations of pellagra are
periodic and its duration indeter¬
minate.

The disease is one the very name
of which was almost unknown in the
United States until within the past
decade. It has usually been regarded
as tropical, though it occurs commonly
in Italy and in various parts of Europe.
Now it is known that it not only
occurs quite generally in the United
vStates but that it is spreading. Lav-
inder (1911) says that “There are
certainly many thousand cases of the
disease in this country, and the pres¬
ent situation must be looked upon
with grave concern.”

It is not within the scope of this book to undertake a general
discussion of pellagra. The subject is of such importance to every
medical man that we cannot do better than refer to Lavinder’s
valuable precis. We can only touch briefly upon the entomological
phases of the problems presented.

The most commonly accepted theories regarding the etiology
of the disease have attributed it to the use of Indian com as an article
of diet. This supposed relationship was explained either on the
basis of, (a) insufficiency of nutriment and inappropriateness of
com as a prime article of food; (b) toxicity of com or, (c) parasitism
of certain organisms — fungi or bacteria — ingested with either sound
or deteriorated com.

In 1905, Sambon proposed the theory of the protozoal origin of
pellagra and in 1910 he marshalled an imposing array of objections
to the theory that there existed any relationship between com and
the disease. He presented clear evidence that pellagra existed in
Europe before the introduction of Indian corn from America, as an

Pellagra

247

article of diet, and that its spread was not pari passu with that of the
use of com. Cases were found in which the patients had apparently
never used com, though that is obviously difficult to establish. He
showed that preventive measures based on the theory had been a
failure. Finally, he believed that the recurrence of symptoms of
the disease for successive springs, inpatients who abstained absolutely
from the use of corn, militated against the theory.

On the other hand, Sambon believed that the periodicity of the
symptoms, peculiarities of distribution and seasonal incidence, and
analogies of the symptoms to those of other parasitic diseases indi-

145. Pellagrous eruption on the hand. After Watson.

cated that pellagra was of protozoal origin, and that it was insect-
borne.

The insect carriers, he believed to be one or more species of
Simuliidse, or black-flies. In support of this he stated that Simulium
appears to effect the same topographical conditions as pellagra,
that in its imago stage it seems to present the same seasonal incidence,
that it has a wide geographical distribution which seems to cover
that of pellagra, and that species of the genus are known to cause
severe epizootics. Concluding from his studies in Italy, that pel¬
lagra was limited almost wholly to agricultural laborers, he pointed
out that the Simulium flies are found only in rural districts, and as a
rule do not enter towns, villages, or houses.

When Sambon’s detailed report was published in 1910, his theory
was seized upon everywhere by workers who were anxious to test it

248

Arthropod Transmission of Disease

146. A favorite breeding place of Simulium. Ithaca, N. Y

Pellagra

249

and who, in most cases, were favorably disposed towards it because
of the wonderful progress which had been made in the understanding
of other insect-borne diseases. In this country, the entomological
aspects of the subject have been dealt with especially by Forbes
(1912), and by King and Jennings, under the direction of W. D.
Hunter, of the Bureau of Entomology, and in co-operation with
the Thompson-McFadden Pellagra Commission of the Department
of Tropical Medicine of the New York Post-Graduate Medical
School. An important series of experiments with monkeys has
been undertaken by S. J. Hunter, of Kansas, but unfortunately we have
as yet no satisfactory evidence that these animals are susceptible
to the disease—a fact which renders the whole problem difficult.

The accumulated evidence is increasingly opposed to Sambon’s
hypothesis of the transmission of pellagra by Simulium. This has
been so clearly manifested in the work of the Thompson-McFadden
Commission that we quote here from the report by Jennings (1914):

“Our studies in 1912 convinced us that there was little evidence
to support the incrimination of any species of Simulium in South
Carolina in the transmission of pellagra. Reviewing the group as a
whole, we find that its species are essentially “wild” and lack those
habits of intimate association with man which would be expected
in the vector of such a disease as pellagra. Although these flies are
excessively abundant in some parts of their range and are moderately
so in Spartanburg County, man is merely an incidental host, and no
disposition whatever to seek him out or to invade his domicile seems
to be manifested. Critically considered, it is nearer the fact that
usually man is attacked only when he invades their habitat.”

“As our knowledge of pellagra accumulates, it is more and more
evident that its origin is in some way closely associated with the
domicile. The possibility that an insect whose association with man
and his immediate environment is, at the best, casual and desultory,
can be active in the causation of the disease becomes increasingly
remote.”

“Our knowledge of the biting habits of Simulium is not complete,
but it is evident, as regards American species at least, that these are
sometimes not constant for the same species in different localities.
Certain species will bite man freely when opportunity offers, while
others have never been known to attack him. To assume that the
proximity of a Simulium -breeding stream necessarily implies that
persons in its vicinity must be attacked and bitten is highly fal-

250 Arthropod Transmission of Disease

laeious. In Spartanburg County attacks by Simulium seems to be
confined to the immediate vicinity of the breeding-places. Our
records and observations, exceedingly few in number, refer almost
exclusively to such locations. Statements regarding such attacks,
secured with much care and discrimination from a large number of
persons, including many pellagrins, indicate conclusively that these
insects are seldom a pest of man in this county. A certain number
of the persons questioned were familiar with the gnats in other
localities, but the majority were seemingly ignorant of the existence
of such flies with biting habits. This is especially striking, in view
of the fact that the average distance of streams from the homes of
the pellagra cases studied was about 200 yards, many being at a
distance of less than 100 yards, and that 78 per cent of these streams
were found to be infested by larval Simulium. Such ignorance in a
large number of persons cannot be overlooked and indicates strongly
that our belief in the negligible character of local attacks by Simulium
is well founded.”

‘‘In localities infested by ‘sand-flies,’ mosquitoes, etc., these
pests are always well known and the ignorance described above is
very significant.”

‘‘Such positive reports as we received nearly always referred to
bites received in the open, along streams, etc., and observations made
of their attack were of those on field laborers in similar situations.
Males engaged in agricultural pursuits are almost exempt from
pellagra in Spartanburg County. During the season of 1913, in
some two or three instances, observations were made of the biting
of Simulium and some additional and entirely creditable reports
were received. These observations and reports were under condi¬
tions identical with those referred to in the reports of 1912 and con¬
firm the conclusions based on the observations of that year. I
would repeat with emphasis that it is inconceivable that a fly of the
appearance and habits of the prevalent species of Simulium could be
present in such a region, especially about the haunts of man and
attack him with sufficient frequency and regularity to satisfactorily
account for so active and prevalent a disease as pellagra without
being a well-known and recognized pest.”

‘‘In connection with the conditions in the Piedmont region of
South Carolina, it may be well to cite the results of a study of those
in the arid region of western Texas.”

Pellagra

251

“In May, 1913, in company with Capt. J. F. Siler of the Thomp-
son-McFadden Pellagra Commission, I visited the region of which
Midland in Midland County is the center. This region is very dry
and totally devoid of running water for a long distance in every
direction. The only natural source of water-supply, a few water
holes and ponds, were visited and found to be of such a nature that
the survival of Simulium, far less its propagation in them, is abso¬
lutely impossible. The nearest stream affording possibilities as a
source of Simulium is 60 miles away, while the average distance of
such possibility is not less than 100 miles.”

“Artificial sources of water-supply were also investigated care¬
fully and were found to offer no opportunity for the breeding of
Simulium."

“At Midland the histories of five cases of pellagra were obtained,
which gave clear evidence that this place or its immediate vicinity
was the point of origin. Persons of long residence in the country
were questioned as to the occurrence of such flies as Simulium and
returned negative answers. These included a retired cattle owner,
who is a man of education and a keen observer, an expert veterinarian
stationed in the country who has the cattle of the country under
constant observation, and a practical cattle man, manager of a ranch
and of wide experience. The latter had had experience with ‘Buf¬
falo gnats’ in other localities (in the East) and is well acquainted
with them. His close personal supervision of the cattle under his
charge, makes it practically certain that he would have discovered
these gnats had they been present in the country.”

“At the time the study was made, Simulium was breeding and
active in the adult state in the vicinity of Dallas, Texas, in the
eastern part of the state. We have here a region in which cases of
pellagra have originated, yet in which Simulium does not and cannot
breed.”

Other possible insect vectors of pellagra have been studied in
great detail and the available evidence indicates that if any insect
plays a role in the spread of the disease, Stomoxys calcitrans most
nearly fills the conditions. This conclusion was announced by
Jennings and King in 1912, and has been supported by their subse¬
quent work.

Yet, after all the studies of the past decade, the old belief that
pellagra is essentially of dietary origin is gaining ground. Gold-
berger, Waring and Willets (1914) of the United States Public Health

252 Arthropod Transmission of Disease

Sendee summarize their conclusions in the statement, (i) that it is
dependent on some yet undetermined fault in a diet in which the
animal or leguminous protein component is disproportionately large
and (2) that no pellagra develops in those who consume a mixed,
well-balanced, and varied diet, such, for example, as that furnished
by the Government to the enlisted men of the Army, Navy, and
Marine Corps.

Leprosy

Leprosy is a specific, infectious disease due to Bacillus lepree, and
characterized by the formation of tubercular nodules, ulcerations,
and disturbances of sensation. In spite of the long time that the
disease has been known and the dread with which it is regarded,
little is known concerning the method of transfer of the causative
organism or the means by which it gains access to the human body.

It is known that the bacilli are to be found in the tubercles, the
scurf of the skin, nasal secretions, the sputum and, in fact in prac¬
tically all the discharges of the leper. Under such conditions it is
quite conceivable that they may be transferred in some instances
from diseased to healthy individuals through the agency of insects
and other arthropods. Many attempts have been made to demon¬
strate this method of spread of the disease, but with little success.

Of the suggested insect carriers none seem to meet the conditions
better than mosquitoes, and there are many suggestions in literature
that these insects play an important role in the transmission of
leprosy. The literature has been reviewed and important experi¬
mental evidence presented by Currie (1910). He found that mosqui¬
toes feeding, under natural conditions, upon cases of nodular leprosy
so rarely, if ever, imbibe the lepra bacillus that they cannot be
regarded as one of the ordinary means of transference of this bacillus
from lepers to the skin of healthy persons. He believes that the
reason that mosquitoes that have fed on lepers do not contain the
lepra bacillus is that when these insects feed they insert their probos¬
cis directly into a blood vessel and thus obtain bacilli-free blood,
unmixed with lymph.

The same worker undertook to determine whether flies are able
to transmit leprosy. He experimented with five species found in
Honolulu, — Musca domestica, Sarcophaga pallinervis, Sarcophaga
barbata, Volucella obesa and an undetermined species of Lucilia.
The experiments with Musca domestica were the most detailed.

Leprosy

253

From these experiments he concluded, first, that all of the above-
named flies, when given an opportunity to feed upon leprous fluids,
will contain the bacilli in their intestinal tracts and feces for several
days after such feeding. Second, that considering the habits of
these flies, and especially those of Musca domestica, it is certain that,
given an exposed leprous ulcer, these insects will frequently convey
immense numbers of lepra bacilli, directly or indirectly, to the skins,
nasal mucosa, and digestive tracts of healthy persons. Additional
evidence along this line has recently been brought forward by
Honeij and Parker (1914), who incriminate both Musca domestica
and Stomoxys calcitrans. Whether or not such insect-borne bacilli
are capable of infecting persons whose skin and mucosa are thus
contaminated, Currie was unwilling to maintain, but he concludes
that until we have more accurate knowledge on this point, we are
justified in regarding these insects with grave suspicion of being
one of the means of disseminating leprous infection.

Various students of the subject have suggested that bed-bugs
may be the carriers of leprosy and have determined the presence of
acid-fast bacilli in the intestines of bed-bugs which had fed on leprous
patients. Opposed to this, the careful experiments of Thompson
(1913) and of Skelton and Parkham (1913) have been wholly nega¬
tive.

Borrel has recently suggested that Demodex, may play a role in
spreading the infection in families. Many other insects and acariens
have been suggested as possible vectors, but the experimental data
are few and in no wise conclusive. The most that can be said is that
it is quite possible that under favorable conditions the infection
might be spread by any of the several blood-sucking forms or by
house-flies.

Verruga peruviana

Verruga peruviana is defined by Castellani and Chalmers as “a
chronic, endemic, specific, general disorder of unknown origin, not
contagious, but apparently inoculable, and characterized by an ir¬
regular fever associated with rheumatoid pains, anemia, followed
by granulomatous swellings in the skin, mucous membranes, and
organs of the body.” It has been generally believed by medical
men interested that the comparatively benign eruptive verruga is
identical with the so-called Oroya, or Carrion’s fever, a malignant
type. This view is not supported by the work of Strong, Tyzzer
and Brues, (1913).

254

Arthropod Transmission of Disease

The disease is confined to South America and to definitely limited
areas of those countries in which it does occur. It is especially
prevalent in some parts of Peru.

The causative organism and the method of transfer of verruga
are unknown. Castellani and Chalmers pointed out in 1910 that the
study of the distribution of the disease in Pem would impress one
with the similarity to the distribution of the Rocky Mountain fever
and would lead to the conclusion that the astiological cause must in
some way be associated with some blood-sucking animal, perhaps an
arachnid, and that this is supported by the fact that the persons
most prone to the infection are those who work in the fields.

More recently, Townsend (1913), in a series of papers, has main¬
tained that verruga and Carrion’s disease are identical, and that they
are transmitted to man by the bites of the Psychodid fly, Phlebotomus
verrucarum. He succeeded in producing the eruptive type of the
disease in experimental animals by injecting a physiological salt
trituration of wild Phlebotomus flies. A cebus monkey was exposed
from October 10 to November 6, by chaining him to a tree in the
verruga zone, next to a stone wall from which the flies emerged in
large numbers every night. Miliar eruption began to appear on the
orbits November 13 and by November 21, there were a number of
typical eruptions, with exudation on various parts of the body
exactly like miliar eruptive sores commonly seen on legs of human
cases.

An assistant in the verruga work, George E. Nicholson, contracted
the eruptive type of the disease, apparently as a result of being bitten
by the Phlebotomus flies. He had slept in a verruga zone, under a
tight net. During the night he evidently put his hands in contact
with the net, for in the morning there were fifty-five unmistakable
Phlebotomus bites on the backs of his hands and wrists.

Townsend believes that in nature, lizards constitute the reservoir
of the disease and that it is from them that the Phlebotomus flies
receive the infection.

Cancer

There are not wanting suggestions that this dread disease is
carried, or even caused, by arthropods. Borrel (1909) stated that
he had found mites of the genus Demodex in carcinoma of the face
and of the mammas. He believed that they acted as carriers of the
virus.

Cancer

255

Saul (1910) and Dahl (1910) go much further, since they attribute
the production of the malignant growth to the presence of mites
which Saul had found in cancers. These Dahl described as belonging
to a new species, which he designated Tarsonemus hominis. These
findings have since been confirmed by several workers. Neverthe¬
less, the presence of the mite is so rare that it cannot be regarded as
an important factor in the causation of the disease. The theory
that cancer is caused by an external parasite is given little credence
by investigators in this field.

In conclusion, it should be noted that the medical and entomolog¬
ical literature of the past few years abounds in suggestions, and in
unsupported direct statements that various other diseases are insect-
borne. Knab (1912) has well said “Since the discovery that certain
blood-sucking insects are the secondary hosts of pathogenic para¬
sites, nearly every insect that sucks blood, whether habitually or
occasionally, has been suspected or considered a possible transmitter
of disease. No thought seems to have been given to the conditions
and the characteristics of the individual species of blood-sucking
insects, which make disease transmission possible.”

He points out that “in order to be a potential transmitter of human
blood-parasites, an insect must be closely associated with man and
normally have opportunity to suck his blood repeatedly. It is not
sufficient that occasional specimens bite man, as, for example, is the
case with forest mosquitoes. Although a person may be bitten by a
large number of such mosquitoes, the chances that any of these
mosquitoes survive to develop the parasites in question, (assuming
such development to be possible), and then find opportunity to bite
and infect another person, are altogether too remote. Applying
this criterion, not only the majority of mosquitoes but many other
blood-sucking insects, such as Tabanidae and Simuliidse, may be
confidently eliminated. Moreover, these insects are mostly in
evidence only during a brief season, so that we have an additional
difficulty of a very long interval during which there could be no prop¬
agation of the disease in question.” He makes an exception of
tick-borne diseases, where the parasites are directly transmitted from
the tick host to its offspring and where, for this reason, the insect
remains a potential transmitter for a very long period. He also
cites the trypanosome diseases as possible exceptions, since the causa¬
tive organisms apparently thrive in a number of different vertebrate
hosts and may be transmitted from cattle, or wild animals, to man.

256

Arthropods Transmission of Disease

Knab’s article should serve a valuable end in checking irrespon¬
sible theorizing on the subject of insect transmission of disease.
Nevertheless, the principles which he laid down cannot be applied
to the cases of accidental carriage of bacterial diseases, or to those
of direct inoculation of pyogenic organisms, or of blood parasites
such as the bacillus of anthrax, or of bubonic plague. Accumulated
evidence has justified the conclusion that certain trypanosomes
pathogenic to man are harbored by wild mammals, and so form an
exception. Townsend believes that lizards constitute the natural
reservoir of verruga; and it seems probable that field mice harbor
the organism of tsutsugamushi disease. Such instances are likely to
accumulate as our knowledge of the relation of arthropods to disease
broadens.

'CHAPTER XII

HOMINOXIOUS ARTHROPODS

The following synoptic tables are presented in the hope that they
may be of service in giving the reader a perspective of the relation¬
ships of the Arthropoda in general and enabling him to identify the
more important species which have been found noxious to man.
Though applicable chiefly to the arthropods found in the United
States, exotic genera and species which are concerned in the trans¬
mission of disease are also included. For this reason the keys to the
genera of the Muscids of the world are given. As will be seen, the
tables embrace a number of groups of species which are not injurious.
This was found necessary in order that the student might not be
lead to an erroneous determination which would result were he to
attempt to identify a species which heretofore had not been considered
noxious, by means of a key containing only the noxious forms. The
names printed in bold faced type indicate the hominoxious arthropods
which have been most commonly mentioned in literature.

CRUSTACEA

Arthropods having two pairs of antennae which are sometimes
modified for grasping, and usually with more than five pairs of legs.
With but few exceptions they are aquatic creatures. Representatives
are: Crabs, lobsters, shrimps, crayfish, water-fleas, and woodlice.
To this class belongs the Cyclops (fig. 122) a genus of minute aquatic
crustaceans of which at least one species harbors Dracunculus medi-
nensis, the Guinea worm (fig. 121).

MYRIAPODA

Elongate, usually vermiform, wingless, terrestrial creatures having
one pair of antennas, legs attached to each of the many intermediate
body segments. This group is divided into two sections, now usually
given class rank: the Diplopoda or millipeds (fig. 13), commonly
known as thousand legs, characterized by having two pairs of legs
attached to each intermediate body segment, and the Chilopoda
or centipeds (fig. 14) having only one pair of legs to each body seg¬
ment.

257

258

Hominoxious Arthropods

ARACHN1DA

In this class the antennae are apparently wanting, wings are never
present, and the adults are usually provided with four pairs of legs.
Scorpions, harvest-men, spiders, mites, etc.

HEXAPODA (Insects)

True insects have a single pair of antennae, which is rarely vestigial,
and usually one or two pairs of wings in the adult stage. Familiar
examples are cockroaches, crickets, grasshoppers, bugs, dragonflies,
butterflies, moths, mosquitoes, flies, beetles, ants, bees and wasps.

ORDERS OF THE ARACHNIDA

a. Abdomen distinctly segmented. A group of orders including scorpions,
(fig. 11), whip-scorpions (fig. 10), pseudo-scorpions, solpugids (fig. 12)

harvest-men (daddy-long-legs or harvestmen), etc. Arthrogastra

aa. Abdomen unsegmented, though sometimes with numerous annulations

.SPHiEROGASTRA

b. A constriction between cephalothorax and abdomen (fig. 7). True Spiders

.Araneida

bb. No deep constriction between these parts.

c. Legs usually well developed, body more or less depressed (fig. 49). Mites

. Acarina

cc. Legs stumpy or absent, body more or less elongate or vermiform, or if
shorter, the species is aquatic or semi-aquatic in habit,

d. Four pairs of short legs; species inhabiting moss or water. Water-

bears . Tardigrada

dd. Two pairs of clasping organs near the mouth, instead of legs, in the
adult; worm-like creatures parasitic within the nasal passages,
lungs, etc. of mammals and reptiles (fig. 148). Tongue worms.
.Linguatulina

Acarina

259

ACARINA*

a. Abdomen annulate, elongate; very minute forms, often with but four legs

(fig. 62).Demodicoidea

b. With but four legs of five segments each. Living on plants, often forming

galls . Eriophyid^e

bb. With eight legs, of three segments each. Living in the skin of mammals

. Demodicid,®

To this family belongs the genus Demodex found in the sebaceous glands
and hair follicles of various mammals, including man. D. phylloides
Csokor has been found in Canada on swine, causing white tubercles
on the skin. D. bovis Stiles has been reported from the United States
on cattle, upon the skin of which they form swellings. D. folliculorum
Simon is the species found on man. See page 78.
aa. Abdomen not annulate nor prolonged behind; eight legs in the adult stage,
b. With a distinct spiracle upon a stigmal plate on each side of the body (usu¬
ally ventral) above the third or fourth coxae or a little behind (fig. 50);
palpi free; skin often coriaceous or leathery; tarsi often with a sucker,

c. Hypostome large (fig. 50), furnished below with many recurved teeth;
venter with furrow's, skin leathery; large forms, usually parasitic

. IXODOIDEA

d. Without scutum but covered by a more or less uniform leathery integu¬
ment; festoons absent; coxae unarmed, tarsi without ventral spurs;
pulvilli absent or vestigial in the adults; palpi cylindrical; sexual

dimorphism slight. Argasid^e

e. Body flattened, oval or rounded, with a distinct flattened margin
differing in structure from the general integument; this margin
gives the body a sharp edge which is not entirely obliterated even
w'hen the tick is full fed. Capitulum (in adults and nymphs)
entirely invisible dorsally, distant in the adult by about its own

length from the anterior border. Eyes absent.Argus Latr.

f. Body oblong; margin with quadrangular cells; anterior tibiae and
metatarsi each about three times as long as broad. On poultry,

southwest United States.A. persicus miniatus

A. brevipes Banks, a species with proportionately shorter legs has
been recorded from Arizona.

ff. With another combination of characters. About six other species
of Argas from various parts of the world, parasitic on birds and
mammals.

ee. Body flattened when unfed, but usually becoming very convex on
distention; anterior end more or less pointed and hoodlike;
margin thick and not clearly defined, similar in structure to the
rest of the integument and generally disappearing on distention;
capitulum subterminal, its anterior portions often visible dorsally
in the adult; eyes present in some species,
f. Integument pitted, without rounded tubercles; body provided
wfith many short stiff bristles; eyes absent. On horses, cattle

and man (fig. 48) . Otiobius Banks.

O.megnini, a widely distributed species, is the type of this genus.
♦Adapted from Banks, Nuttall, Warburton, Stiles, et . al .

260

Hominoxious A rth ropods

ff. Integument with rounded tubercles or granules; body without stiff

bristles.Omithodoros Koch.

g. Two pairs of eyes; tarsi IV with a prominent sub terminal spur
above; leg I strongly roughened. On cattle and man.

.O. coriaceus

gg. No eyes; no such spur on the hind tarsi.

h. Tarsi I without humps above. O. talaje.

lih. Tarsi I with humps above.

i. Tarsi IV without distinct humps above. On hogs, cattle

and man.O. turicata

ii. Tarsi IV with humps nearly equidistant (fig. 142). Africa.

. O. moubata

dd. With scutum or shield (fig. 50); festoons usually present; coxa?
usually armed with spurs, tarsi generally with one or two ventral
spurs; pulvilli present in the adults; sexual dimorphism pronounced

. IXODIDiE

e. With anal grooves surrounding anus in front; inornate; without eyes;
no posterior marginal festoons; venter of the male with non¬
salient plates. Numerous species, 14 from the United States,
among them I. ricinus (fig. 49 and 50), scapularis, cookei, hexa-
gonus, bicornis. Ixodes Latr. (including Ceratixodes).

ee. With anal groove contouring anus behind, or groove faint or obsolete,

f. With short palpi (fig. 149).

g. Without eyes, inornate, with posterior marginal festoons; male
without ventral plates. Numerous species. II. chordeilis

and leporis-palustris from the United States .

. Hmmaphysalis Koch.

Acarina

261

loO. Stigmal plate of Dermacentor andersoni; (a) of male, (6) of female. After Stiles.

(c) Dermacentor variabilis, male - ( d ) Glyciphagus obesus; ( e ) Otodectes
cynotis; (/) Tyroglyphus lintneri; (g) Tarsonemus pallidus; (h) anal plate
and mand’ble of Liponyssus; (c) to ( h ) after Banks.

262

Hominoxious A rthropods

gg. With eyes.

h. Anal groove distinct; posterior marginal festoons present,

i. Base of the capitulum (fig. 150c) rectangular dorsally;

usually ornate.Dermacentor Koch.

j. Adults with four longitudinal rows of large denticles on
each half of hypostome; stigmal plate nearly circular,
without dorso-lateral prolongation, goblets very large,
attaining 43/* to 115/^ in diameter; not over 40 per
plate, each plate surrounded by an elevated row of
regularly arranged supporting cells; white rust want¬
ing; base of capitulum distinctly broader than long,
its postero-lateral angles prolonged slightly, if at all;
coxae I with short spurs; trochanter I with small
dorso-terminal blade. Texas, Arizona, etc. D. nitens

151. Rhipicephalus bursa, male.
After Nuttall and Warburton.

jj. Adults with three longitudinal rows of large denticles on
each half of hypostome; goblet cells always more
than 40 per plate; whitish rust usually present,

k. Dorso-lateral prolongation of stigmal plate small or
absent; plates of the adults distinctly longer than
broad; goblet cells large, usually 30/u to 85M in
diameter, appearing as very coarse punctations on
untreated specimens, but on specimens treated
with caustic potash they appear very distinct in
outline; base of capitulum distinctly (usually about
twice) broader than long, the postero-lateral angles
distinctly produced caudad; spurs of coxae I long,
lateral spur slightly longer than median; tro¬
chanter I with dorso-terminal spur. D. albipictus,
(= variegatus), salmoni, nigrolineatus.

Acarina

263

kk. Dorsolateral prolongation of stigmal plate distinct.

I . Body of plate distinctly longer than broad; goblet

cells of medium size, usually 17.5M to 35/x or 40M in
diameter, appearing as medium sized punctua¬
tions on untreated specimens, but on the speci¬
mens treated with caustic potash they appear
very distinct in outline, which is not circular;
base of capitulum usually less than twice as broad
as long, the postero-lateral angles always dis¬
tinctly prolonged caudad.

m. Trochanter I with distinct dorso-subterminal
retrograde sharp, digitate spur; postero¬
lateral angles of capitulum pronouncedly
prolonged caudal, 112/x to 160 m long; goblet
cells attain 13M to 40 m in diameter; type

locality California.D. occidentalis

mm. Trochanter I with dorso-terminal blade; postero¬
lateral angles of capitulum with rather short
prolongations.

n. Stigmal plate small, goblet cells not exceeding
45 in the male or 100 in the female; scutum
with little rust, coxa I with short spurs, the
inner distinctly shorter than the outer

. D. parumapertus-marginatus

nn. Stigmal plate larger; goblet cells over 70 in
the male and over 100 in the female; coxa I
with longer spurs, inner slightly shorter
than the outer; scutum with considerable
rust.D. venustus*

II . Goblet cells small, rarely exceeding 17.6 m, occasional¬

ly reaching 19M in diameter; on untreated speci¬
mens they appear as very fine granulations, and on
specimens treated with caustic potash they may
be difficult to see, but their large number can
be determined from the prominent stems of the
goblets; surface of outline of the goblets dis¬
tinctly circular; base of the capitulum usually less
than twice as broad as long, the postero-lateral
angle distinctly prolonged caudad; spurs of

coxae I long.

. D. reticulatus and electus (= variabilis?)

ii. Base of the capitulum (fig. 151) usually hexagonal (except
in the male of puchellus ); and usually inornate.

*Dr. C. W. Stiles considers the species which is responsible for spotted fever distinct from the
venustus of Banks, separating it as follows:

Goblet cells about 75 in the male or 105 in the female. Texas. D. venustus.

Goblet cells 157 in the male, or 120 in the female; stigmal plate shaped as shown in the figure
(figs. 150 a, b). Montana, etc. D. andersoni.

264

Hominoxious Arthropods

j. No ventral plate or shield in either sex (fig. 153). R.

bicomis from the United States ... Rhipicentor Nuttall
jj. Males with a pair of adanal shields, and usually a pair of
accessory adanal shields. Numerous species, among
them R. sanguineus (fig. 154) and texanus, the latter

from the United States. Rhipicephalus Koch

hh. Anal grooves faint or obsolete; no marginal festoons.

i. Short palpi; highly chitinized; unfed adults of large size;
coxae conical; male with a median plate prolonged in two
long spines projecting caudad; segments of leg pair IV

greatly swollen (fig. 155, 156). M. winlhemi .

. Margaropus Karsch

152 . Monieziella (Histiogaster) emtomophaga-spermatica, ventral aspect,
male and female. After Trouessart,

ii. Very short palpi, ridged dorsally and laterally; slightly
chitinized; unfed adults of smaller size; coxae I bifid;
male with adanal and accessory adanal shields (fig. 139).

B. annulatus.Boophilus Curtis

ff. Palpi longer than broad (fig. 157).

g. Male with pair of adanal shields, and two posterior abdominal
protrusions capped by chitinized points; festoons present or
absent. Several species, among them H. aegypticum (fig. 140)

from the old world.Hyalomma Koch

gg. Male without adanal shields but small ventral plaques are
occassionally present close to the festoons. Many species, a
few from the Unted States (fig. 157). . . . Amblyomma Koch
h. Coxa I with but one spine; metatarsi (except 1 ) with two

thickened spurs at tips . A. maculatum

hh. Coxa I with two spines; metatarsi without stout spurs at
tips, only slender hairs.

Acarina

265

i. Projections of coxa I blunt and short. Large species on the

gopher tortoise in Florida. A. tuberculatum

ii. Projections of coxa I longer, and at least one of them sharp

pointed; second segment of palpus twice as long as the
third; coxa IV of the male with a long spine,
j. Porose areas nearly circular; shield of both sexes pale
yellowish, with some silvery streaks and marks, and
some reddish spots; shield of female as broad as long.

.A. cajennense ( = mixtum).

jj. Porose areas elongate, shield brown, in the female with
an apical silvery mark, in the male with two small
and two or four other silvery spots; shield of the fe¬
male longer than broad (fig 158 e). .A. americanum.

internal spur
Exttrn&l spu^n

Kcc 31
Ccxjx- ?rr
CmcxK 2 Y.

•Spi cac /e—

153 . Rhipicentor bicornis, ventral aspect, male. After Nuttall and
Warburton.

rrcPcoC

:. Hypostome small, without teeth, venter without furrows; body often
with coriaceous shields, posterior margin of the body never crenulate

(i.e. without festoons); no eyes.GAMASOIDEA.

d. Parasitic on vertebrates; mandibles fitted for piercing; body sometimes

constricted . Dermanyssid^e.

e. Anal plate present. DERMANYSSiNbE.

f. Body short; legs stout, hind pair reaching much beyond the tip of

the body. On bats. Pteroptus Dufour.

ff. Body long; hind legs not reaching beyond the tip of the body,

g. Peritreme on the dorsum, very short; body distinctly con¬
stricted . Ptilonyssus Berl.

gg. Peritreme on the venter, longer; body not distinctly con¬
stricted.

h. Mandibles in both sexes chelate. Parasitic on bats, mice

and birds (fig. 150, h).Liponyssus Kol.

The species L. (= Leiognathus) sylviarum frequents the
nests of warblers. An instance is on record of these mites
attacking man, causing a pruritis.

266

Hominoxious Arthropods

hh. Mandibles in the male chelate (fig. 158 j), in the female long,

styliform. Parasitic on birds.Dermanyssus Dug.

Two species of importance may be noted, D. hirundinus
and D. gallinae. The latter (fig. 51) is a serious pest
of poultry, sometimes attacking man, causing itching
and soreness.

ee. Anal plate absent. In lungs and air passages of some mammals.

. Halarachnin^;.

dd. Free or attached to insects, rarely on vertebrates.

e. First pair of legs inserted within the same body opening as the oral
tube; genital apertures surrounded by the sternum. On in¬
sects . Uropodid^e.

154 . Rhieephalus sanguineus, male.

After Nuttall and Warbur-
ton.

ee. First pair of legs inserted at one side of the mouth opening; male
genital aperture usually on the anterior margin of the sternal

plate .Gamasidae.

This family contains a number of genera, some of which are found
upon mammals, though the majority affect only other artho-
pods. One species, Laelaps stabularis, frequents the bedding
in stables, and in one instance at least, has occasioned irri¬
tation and itching, in man.

bb. No distinct spiracle in the stigmal plate on each side of the body.

c. Body usually coriaceous, with few hairs, with a specialized seta arising
from a pore near each posterior corner of the cephalothorax; no eyes;
mouth parts and palpi very small; ventral openings of the abdomen

large; tarsi without sucker. Not parasitic.ORIBATOIDEA.

cc. Body softer; without such specialized seta.

d. Aquatic species.HYDRACHNOIDEA

dd. Not aquatic.

A carina

267

. Palpi small, three segmented, adhering for some distance to the lip;
ventral suckers at genital opening or near anal opening usually
present; no eyes; tarsi often end in suckers; beneath the skin on
the venter are seen rod-like epimera that support the legs; body
often entire. Adults frequently parasitic. .. .SARCOPTOIDEA.

f. With tracheae; no ventral suckers; legs ending in claws; body
divided into cephalothorax and abdomen; the female with a
clavate hair between legs I and II. Usually not parasitic

on birds and mammals. Tarsonemid.®

g. Hind legs of female ending in claw and sucker as in the other

pairs. Pediculoidin je

To this sub-family belongs the genus PEDICUXOIDES
P. ventricosus is described on page 69.

155. Margaropus winthemi, male. After 156. Margaropus winthemi,
Nuttall and Warburton. capitulum and scutum,

After Nuttall and War-
burton.

gg. Hind legs of the female end in long hairs. TarSONEMINjE

Tarsonemus intectus Karpelles, normally found upon grain,
is said to attack man in Hungary and Russia. Other
species of the genus affect various plants (c.f. fig. 150, g).
ff. Without tracheae; no such clavate hair.

g. Genital suckers usually present; integument usually without
fine parallel lines.

h. Legs short, without clavate hair on tarsi I and II. On

insects. Canestrinid^e.

hh. Legs longer, with a clavate hair on tarsi I and II, Not

normally parasitic except on bees. Tyroglyphid^e

i Dorsal integument more or less granulate; claws very weak,
almost invisible; some hairs of the body plainly feathered;

ventral apertures large.Glyciphagus Her.

This genus occurs in the United States. In Europe the
mites have been found feeding on all sorts of substances.
They are known as sugar mites and cause the disease

268

Hominoxious A rth ropods

known as grocer’s itch. G. domesticus and G. pru-
norum are old world species (fig. 150, d).
ii. Dorsal integument not granulate; claws distinct; no
prominent feathered hairs; ventral aperture small,

j. Mandibles not chelate; elongate, and toothed below;
body without long hairs; palpi enlarged at tip and
provided with two divergent bristles. Species feed on

decaying substances. Histiostoma Kram.

jj. Mandibles chelate; palpi not enlarged at the tip, nor
with two bristles.

k. No clavate hair on the base of tarsi I and II; no
suture between cephalothorax and abdomen. Live

on bees or in their nests. Trichotarsus Can.

kk. A clavate or thickened hair at the base of tarsi I and II.

I . The bristle on the penultimate segment of the legs

arises from near the middle; no suture between the
cephalothorax and abdomen. The species, some
of which occur in the United States, feed on dried
fruit, etc. Ccirpoglyphus Robin.

II . The bristle on the penultimate segment of the legs

arise from near the tip; a suture between cephalo¬
thorax and abdomen.

m. Cephalothorax w r ith four distinct and long bristles
in a transverse row; tarsi I and II about twice
as long as the preceding segment (fig. 150 f)

.Tyroglyphus Latr.

n. Some bristles on tarsi I and II near middle,
distinctly spine-like; the sense hair about its
length from the base of the segment. Several
species in the United States belong to this
group.

nn. No spine-like bristles near the middle of the
tarsi; sense hair not its length from the base
of the segment.

o. Of the terminal abdominal bristles, only two
are about as long as the abdomen; 1 eg I
of the male greatly thickened and with a
spine at apex of the femur below. . T. farinas.
00. Of the terminal abdominal bristles at least
six or more are very long, nearly as long
as the body.

p. Bristles of the body distinctly plumose or
pectinate; tarsi very long. . T. longior.
pp. Bristles of the body not pectinate.

q. In mills, stored foods, grains, etc. Third
and fourth joints of hind legs scarcely
twice as long as broad; abdominal
bristles not unusually long; legs I

Acarina

269

and II of the male not unusually

stout. T. americanus.

qq. With other characters and habits.
T. lintneri (fig. 150 f) the mushroom
mite, and several other species,
mm. Cephalothorax with but two long distinct
bristles (besides the frontal pair), but some¬
times a very minute intermediate pair;
tarsi I and II unusually short and not twice
as long as the preceding segment,
n. Tarsi with some stout spines. Rhizoglyphus Clap.
The species of this genus are vegetable feed¬
ers. Several occur in the United States.
R. parsiticus and R. spinitarsus have been
recorded from the old world, attacking human
beings who handle affected plants,
nn. Tarsi with only fine hairs. . Monieziella Berl.
The species of this genus, as far as known,
are predaceous or feed on recently killed
animal matter. Several species occur
in the United States. M. (= Histiogaster)
entomophaga (fig. 152) from the old
world has been recorded as injurious
to man.

gg. Genital suckers absent; integument with fine parallel lines.
Parasitic on birds and mammals,
h. Possessing a specially developed apparatus for clinging to

hairs of mammals. Listrophorid.e.

hh. Without such apparatus.

i. Living on the plumage of birds . Analgesid.-e.

ii. In the living tissues of birds and mammals.

j. Vulva longitudinal. In the skin and cellular tissues of

birds. Cytoleichid.e.

This family contains two species, both occurring in the
United States on the common fowl. Laminosioples
cysticola occurs on the skin and also bores into the
subcutaneous tissue where it gives rise to a cal¬
careous cyst. Cytoleichus nudus is most commonly
found in the air passages and air cells,
jj. Vulva transverse. In the skin of mammals and birds

. SARCOPTIDjE

k. Anal opening on the dorsum.

I . Third pair of legs in the male without apical suckers.

On cats and rabbits . Notoedres Rail.

The itch mite of the cat, N. cati (fig. 61) has been
recorded on man.

II . Third leg in the male with suckers. On bats. . . .

. Prosopodectes Can.

270

Hominoxious Arthropods

kk. Anal opening below.

I . Pedicel of the suckers jointed; mandibles styliform

and serrate near the tip . Psoroptes Gerv.

P. communis ovis is the cause of sheep scab.

II . Pedicel of the suckers not jointed; mandibles
chelate.

m. No suckers on the legs of the females; parasitic
on birds, including chickens. C. mutans is
itch mite of chickens. Cnemidocoptes Furst.
mm. Suckers at least on legs I and II; parasitic on
mammals.

n. Legs very short; in the male the hind pairs

equal in size; body usually short .

. Sarcoptes Latr.

S. scabiei is the itch mite of man (fig. 56).

157. Amblyomma, female. After Nuttall
and Warburton.

nn. Legs more slender; in the male the third pair
is much larger than the fourth; body more
elongate.

o. Female w r ith suckers on the fourth pair of
legs. Species do not burrow in the skin,
but produce a scab similar to sheep scab.
They occur in the ox, horse, sheep and goat

.Chorioptes Gerv.

C. symbiotes bovis of the ox has been
recorded a few times on man.

00. Female without suckers to the fourth legs,

p. Hind part of the male abdomen with two

lobes. On a few wild animals .

. Caparinia Can.

Acarina

271

pp. Hind part of the male abdomen without
lobes. Live in ears of dogs and cats

.. . Otodectes Canestr.

0 . cynotis Hering (fig. 150 e) has been
taken in the United States.

:. Palpi usually of four or five segments, free; rarely with ventral
suckers near genital or anal openings; eyes often present; tarsi
never end in suckers; body usually divided into cephalothorax
and abdomen; rod-like epimera rarely visible; adults rarely
parasitic.

f. Last segment of the palpi never forms a thumb to the preceding
segment; palpi simple, or rarely formed to hold prey; body

with but few hairs.EUPODOIDEA.

g. Palpi often geniculate, or else fitted for grasping prey; mandi¬
bles large and snout like; cephalothorax with four long
bristles above, two in front, two behind; last segment of leg I

longer than the preceding segment, often twice as long.

. BdELLID/E.

gg. Palpi never geniculate (fig. 158a), nor fitted for grasping prey:
beak small; cephalothorax with bristles in different arrange¬
ment; last segment of leg I shorter or but little longer than
the preceding joint; eyes when present near posterior

border . Eupodid^e

Moniez has described a species from Belgium (Tydeus

molestus) which attacks man. It is rose colored; eye¬
less; its legs are scarcely as long as its body, the hind
femur is not thickened; the mandibles are small and the
anal opening is on the venter. The female attains a
length of about 0.3 mm.

ff. Last segment of the palpus forms a thumb to the preceding, which
ends in a claw (with few exceptions); body often with many

hairs (fig. 158 k).TROMBIDOIDEA.

g. Legs I and II with processes bearing spines; skin with several

shields; coxae contiguous.C/ECULID.E.

gg. Legs I and II without such processes; few if any shields,

h. Palpi much thickened on the base, moving laterally, last
joint often with two pectinate bristles; no eyes; legs I
ending in several long hairs; adult sometimes parasitic
.CHEYLETIDiE

Cheyletus eruditus, which frequents old books, has once
been found in pus discharged from the ear of man.
hh. Palpi less thickened, moving vertically; eyes usually present;
leg I not ending in long hairs.

i. Coxae contiguous, radiate; legs slender, bristly; body with

few hairs; no dorsal groove; tarsi not swollen .

. Erythr.eid.e.

ii. Coxae more or less in two groups; legs less bristly.

272

Hominoxious Arthropods

158. (a) Tydeus, beak and leg from below; (b) Cheyletus pyriformis, beak and palpus:

(c) beak and claw of Pediculoides; ( d) leg of Sarcoptes; (e) scutum of
female of Amblyomma americana; (/) leg i and tip of mandible of Histio-
stoma americana; (g) Histiogaster malus, mandible and venter; ( h ) Aleuro-
bius farinae, and leg i of male: (*) Otodectes cynotis. tip of abdomen of male,
(j) beak and anal plate of Dermanyssus gallinae; ( k ) palpus of Allothrom-
bium. (a) to (j) after Banks.

A carina

273

j. Body with fewer, longer hairs; often spinning threads;
no dorsal groove; tarsi never swollen; mandibles

styhform (for piercing). TETRANYCHID®

The genus Tetranychus may be distinguished from the
other genera occurring in the United States by the
following characters: No scale-like projections on
the front of the cephalothorax; legs I as long or
longer than the body; palp ends in a distinct thumb;
the body is about 1.5 times as long as broad. T.
molestissimus Weyenb. from South America, and
T. telarius from Europe and America ordinarily
infesting plants, are said also to molest man.
jj. Body with many fine hairs or short spines; not spinning
threads; often with dorsal groove; tarsi often
swollen.

k. Mandibles styliform for piercing. . . . Rhycholophid.-e.

kk. Mandibles chelate, for biting. TROMBIDID®

The genus Trombidium has recently been sub¬
divided by Berlese into a number of smaller
ones, of which some five or six occur in the
United States. The mature mite is not para¬
sitic but the larvae which are very numerous in
certain localities will cause intense itching,
soreness, and even more serious complications.
They burrow beneath the skin and produce
inflammed spots. They have received the
popular name of “red bug,” The names Leptus
americanus and L. irritans have been applied to
them, although they are now known to be im¬
mature stages. (Fig. 44.)

HEXAPODA (Insecta)

The Thysanura (springtails and bristletails), the Neuropteroids
(may-flies, stone-flies, dragon-flies, caddis-flies, etc.), Mallophaga
(bird lice), Phvsopoda (thrips), Orthoptera (grasshoppers, crickets,
roaches), are of no special interest from our viewpoint. The remain¬
ing orders are briefly characterized below.

SIPHUNCULATA (page 275)

Mouth parts suctorial; beak fleshy, not jointed; insect wingless;
parasitic upon mammals. Metamorphosis incomplete. Lice.

HEMIPTERA (page 275)

Mouth parts suctorial; beak or the sheath of the beak jointed;
in the mature state usually with four wings. In external appearance

274

Hominoxious Arthropods

the immature insect resembles the adult except that the immature
form (i. e. nymph) never has wings, the successive instars during
the process of growth, therefore, are quite similar; and the meta¬
morphosis is thus incomplete. To this order belong the true bugs,
the plant lice, leaf hoppers, frog hoppers, cicadas, etc.

LEPIDOPTERA

The adult insect has the body covered with scales and (with the
rare exception of the females of a few species) with four wings also
covered with scales. Proboscis, when present, coiled, not seg¬
mented, adapted for sucking. Metamorphosis complete, i.e. the
young which hatches from the egg is quite unlike the adult, and after
undergoing several molts transforms into a quiescent pupa which is
frequently enclosed in a cocoon from which the adult later emerges.
The larvae are known as caterpillars. Butterflies and moths.

DIPTERA (page 285)

The adult insect is provided with two, usually transparent,
wings, the second pair of wings of other insects being replaced by a
pair of halteres or balancers. In a few rare species the wings, or
halteres, or both, are wanting. The mouth parts, which are not
segmented, are adapted for sucking. The tarsi are five-segmented.
Metamorphosis complete. The larva?, which are never provided
with jointed legs, are variously known as maggots, or grubs, or
wrigglers. Flies, midges, mosquitoes.

SIPHONAPTERA (page 316)

Mouth parts adapted for sucking; body naked or with bristles
and spines; prothorax well developed; body compressed; tarsi
with five segments; wings absent. Metamorphosis complete.
The larva is a wormlike creature. Fleas.

COLEOPTERA

Adult with four wings (rarely wanting), the first pair horny or
leathery, veinless, forming wing covers which meet in a line along
the middle of the back. Mouth parts of both immature stages and
adults adapted for biting and chewing. Metamorphosis complete.
The larvae of many .species are known as grubs. Beetles.

Siphunculata and Hemiptera

2 75

HYMENOPTERA

Adult insect with four, usually transparent, wings, wanting in
some species. Mouth parts adapted for biting and sucking; palpi
small; tarsi four or five-segmented. Metamorphosis complete.
Parasitic four-winged flies, ants, bees, and wasps.

SIPHUNCULATA AND HEMIPTERA

a. Legs with claws fitted for clinging to hairs; wings wanting; spiracles of the

abdomen on the dorsal surface. ( = ANOPLURA = PARASITICA).

.SIPHUNCULATA.

b. Legs not modified into clinging hooks; tibia and tarsus very long and
slender; tibia without thumb-like process; antennae five-segmented

.H^matomyzid.e Endr.

Hczmatomyzus elephantis on the elephant,
bb. Legs modified into clinging hooks; tibia and tarsus usually short and
stout; tibia with a thumb-like process; head not anteriorly pro¬
longed, tube-like.

c. Body depressed; a pair of stigmata on the mesothorax, and abdominal
segments three to eight; antennae three to five-segmented,

d. Eyes large, projecting, distinctly pigmented; pharynx short and
broad; fulturae (inner skeleton of head) very strong and broad,
with broad arms; proboscis short, scarcely attaining the thorax.

.PEDICULIDiE

e. Antenna; three-segmented. A few species occurring upon old

world monkeys. Pedicinis Gerv.

ee. Antennae five -segmented.

f. All legs stout; thumb-like process of the tibia very long and
slender, beset with strong spines, fore legs stouter than the
others; abdomen elongate, segments without lateral pro¬
cesses; the divided telson with a conical process posteriorly

upon the ventral side.Pediculus L.

g. Upon man,

h. Each abdominal segment dorsally with from one to three
more or less regular transverse rows of small setae;
% antenna about as long as the width of the head. Head

louse (fig. 65).P. humanus.

hh. “No transverse rows of abdominal setae; antenna longer
than the width of the head; species larger.” Piaget.

Body louse of man.P. corporis.

gg. Upon apes and other mammals. P. pusitatus (?).

ff. Fore legs delicate, with very long and slender claws; other legs
very stout with short and stout claws; thumb-like process of
the tibia short and stout; abdomen very short and broad;
segment one to five closely crowded, thus the stigmata of seg¬
ments three to five apparently lying in one segment; segments
five to eight with lateral processes; telson without lateral

conical appendages (fig. 69). Crab louse of man .

.Phthirus pubis.

276

Hominoxious Arthropods

dd. Eyes indistinct or wanting; pharynx long and slender, fulturae very
slender and closely applied to the pharynx; proboscis very long.

Several genera found upon various mammals. H;ematopinid.;e.

cc. Body swollen; meso- and metathorax, and abdominal segments two to
eight each with a pair of stigmata; eyes wanting; antennae four or
five-segmented; body covered with stout spines. Three genera found

upon marine mammals. Echinophthiriid^e

aa. Legs fitted for walking or jumping; spiracles of abdomen usually ventral;
beak segmented.

b. Apex of head usually directed anteriorly; beak arising from its apex; sides
of the face remote from the front coxae; first pair of wings when present
thickened at base, with thinner margins.HETEROPTERA

c. Front tarsi of one segment, spade-form (pakeformes); beak short, at
most two-segmented; intermediate legs long, slender; posterior pair

adapted for swimming.CoRixiDiE

ec. Front tarsi rarely one-segmented, never spade-form; beak free, at least
three-segmented,

d. Pulvilli wanting.

e. Hemelytra usually with a distinct clavus (fig. 159), clavus always
ends behind the apex of the scutellum, forming the commissure.
(Species having the wings much reduced or wanting should be
sought for in both sections.)

f. Antenna; very short; meso- and metasternum composite; eyes
always present.

Siphunculata and Hemiptera

277

g. Ocelli present; beak four-segmented. Ochterid/E and
Nerthrioe.

gg. Ocelli wanting; antennae more or less hidden in a groove,

h. Anterior coxae inserted at or near anterior margin of the
prostemum; front legs raptorial; beak three-segmented.
Belostomid^e (withswimming legs), Nepid/e, Naucorid.e.

i. Metasternum without a median longitudinal keel; antennae
alw'ays four -segmented.

j. Beak short, robust, conical; the hairy fleck on the corium
elongate, large, lying in the middle between the inner
angle of the membrane and the outer vein parallel to
the membrane margin; membrane margin S-shaped.

k. The thick fore femur with a relatively deep longitudinal
furrow to receive the tibia. Several American
species (fig. 19f.). . .Belostoma ( = Lethocerus Mayer)
kk. The less thickened fore femur without such a furrow

.B. griseus. Benacus Stal.

jj. Beak slender, cylindrical; the hairy spot on the corium
rounded lying next to the inner angle of the membrane,
k. Membrane large, furrow of the embolium broadened.

Z. aurantiacum, fluminea, etc. Zaitha

kk. Membrane very short; furrow of embolium not
broadened. Western genus. Pedinocoris

ii. Metasternum with a long median longitudinal keel. South¬
western forms. A bedus ovatus and Deniostoma dilatato

hh. Anterior coxae inserted at the posterior margin of the
prosternum; legs natatorial. Back swimmers (fig. 19 b.)
. NOTONECTIDjE

i. Apices of the hemelytra entire; the three pairs of legs

similar in shape; beak three-segmented; abdomen not
keeled or hairy. Plea Leach

ii. Apices of hemelytra notched; legs dissimilar; beak four-

segmented; abdomen keeled and hairy,
j. Hemelytra usually much longer than the abdomen;
fourth segment of the antenna longer than the third

segment; hind tarsi with claws . Bueno Kirk.

jj. Hemelytra but little longer than the abdomen; fourth
segment of the antenna shorter than the third seg¬
ment; hind tarsi without claws (fig. 19b). . Notonecta L.
ff. Antennae longer than the head; or if shorter, then the eyes and
ocelli absent.

g. Eyes, ocelli, and scutellum wanting; beak three-segmented;
head short; hemelytra always short; membrane wanting.

Insects parasitic on bats. Polyctenid.e

gg. Eyes present.

h. First tw r o antennal segments very short, last two long, pilose,
third thickened at the base; ocelli present, veins of the
hemelytra forming cells. Dipsocorid.e ( = Ceratocombi-
d.e) including Schizopterid.e.

Hominoxious A rthropods

hh. Third segment of the antenna not thickened at the base,
second as long or longer than the third, rarely shorter,

i. Posterior coxae hinged (cardinate), if rarely rotating, the
cuneus is severed, the membrane is one or two-celled,
and the meso- and metastemum are composite,

j. Ocelli absent, clypeus dilated toward the apex; hemelvtra
always short, membrane wanting. Species parasitic.

Bed bugs, etc. ClMlClDiE

k. Beak short, reaching to about the anterior coxae;
scutellum acuminate at the apex; lateral margin of
the elytra but little reflexed, apical margin more or
less rounded; intermediate and posterior coxae
very remote.

1 . Body covered with short hairs, only the sides of the
pronotum and the hemelytra fringed with longer
hairs; antennae with the third and fourth seg¬
ments very much more slender than the first and
second; pronotum with the anterior margin very

deeply sinuate .Cimex L.

m. Sides of the pronotum widely dilated, broader
than the breadth of one eye, and densely
fringed with backward curved hairs; apical
margin of the hemelytra nearly straight, rounded
toward the interior or exterior angles,

n. Body covered with very short hairs; second
segment of the antenna shorter than the third;
sides of the pronotum feebly reflexed, fringed
with shorter hairs than the breadth of one
eye; hemelytra with the commissural (inner)
margin rounded and shorter than the scutel¬
lum, apical margin rounded towards the
interior angle. The common bed bug (fig.

19I1).C. lectularius Linn

nn. Body covered with longer hairs; second and
third segments of the antenna of equal
length; side of the pronotum narrowly, but
distinctly, reflexed, fringed with longer
hairs than the breadth of one eye; hemelytra
with the commissural margin straight and
longer than the scutellum, apical margin
rounded towards the exterior angle. Species
found on bats in various parts of the United

States. C. pillosellus Hov.

mm. Sides of the pronotum neither dilated, nor
reflexed, fringed with less dense and nearly
straight hairs; hemelytra with the apical
margin distinctly rounded. Parasitic on
man, birds and bats. Occurs in the old

world, Brazil and the West Indies .. .

. C. hemipterus Fabr. ( = rotundatus)

Siphunculata and Hemiptera

279

11 . Body clothed with rather longer silky hairs; third
and fourth segments of the antenna somewhat
more slender than the first and second; anterior
margin of the pronotum very slightly sinuate or
nearly straight in the middle, produced at the
lateral angles. This is the species which in Ameri¬
can collections is known as C. hirundinis, the
latter being an old world form. It is found in
swallow's nests. O. vicarius. .. Oeciacus Slal
kk. Beak long, reaching to the posterior coxas; scutellum
rounded at the apex; lateral margins of the elytra
strongly reflexed, apical margin slightly sinuate
tow'ard the middle; intermediate and posterior
coxae sub-contiguous. This species infests poultry
in southwest United States and in Mexico. H.
inodorus.Haematosiphon Champ.

160. Pselliopsis (Milyas)
cinctus. (x 2 ). After
C. V. Riley.

jj. Ocelli present, if rarely absent in the female, then the
tarsus has two segments; or if with three tarsal seg¬
ments, the wing membrane with one or two cells,
k. Beak four-segmented, or with tw'o-segmented tarsi.

. .Isometopid^e, Microphysid.e and some Capsids.
kk. Beak three-segmented.

I . Hemelytra with embolium; head horizontal, more

or less conical; membrane with one to four veins,

rarely W'anting.ANTHOCORIDjE

Several species of this family affecting man have
been noted, Anthocoris kingi and congolense,
from Africa and Lyctocoris campestris from
various parts of the world. Lyctocoris fitchii
Reuter (fig. 19 j), later considered by Reuter as
a variety of L. campestris, occurs in the United
States.

II . Hemelytra wdthout embolium. Superfamily Acan-

thioidea ( = Sald^e Fieber and Leptopod.e
Fieber)

2So

Hominoxious Arthropods

ii. Posterior coxa; rotating.

j. Claws preapical; aquatic forms. Gerrid® and Veliad®
jj. Claws apical.

k. Prosternum without stridulatory sulcus (notch for
beak).

I. Tarsus with three segments; membrane with two or

three longitudinal cells from which veins radiate;
rarely with free longitudinal veins (Arachnocoris)
or veins nearly obsolete (Arbela); clavus and
corium coriaceous; ocelli rarely absent. . Nabid®
Reduviolus ( = Coriscus) subcoleoptratus (fig. 19 g),
a species belonging to this family, occurring in
the United States, has been accused of biting
man. This insect is flat, of a jet black color,
bordered with yellow on the sides of the abdomen,
and with yellowish legs. It is predaceous,
feeding on other insects.

II. With other combinations of characters. Hydro-

METRID®, HENICOCEPHALID®, N®OGEID®, MESO-
VELIAD®, JOPPEICID®

kk. Prosternum with stridulatory sulcus (notch for beak);
with three segments, short, strong.

I. Antennae filiform or sometimes more slender apically,

geniculate; wing membrane with two or three
large basal cells; scutellum small or moderate

.REDUVIID®

For a key to the genera and species see next page.

II. Last antennal segment claVhte or fusiform; wing

membrane with the veins often forked and ana¬
stomosing; scutellum large; tarsi each with two
segments; fore legs strong. ( = Phy t matid®)

. Macrocephalid.e

ee. Clavus noticeably narrowed towards the apex, never extending
beyond the scutellum, the two not meeting to form a commissure;
head horizontal, much prolonged between the antennse, on each
side with an antennal tubercle, sometimes acute; ocelli absent;
meso- and metasternum simple; tarsi each with two segments;
body flattened (fig. 19c). Aradid®, including Dysodiid®.
dd. Pulvilli present (absent in one Australian family THAuM atocorid ®
in which case there is a membranous appendage at the tip of the
tibia). Capsid.® ( = Mirid®),* Eotrechus (in family Gerrid®),
N®ogaid®, Tingitid®, Piesmid®, Myodochid®, Corizid®,
Coreid®, Alydid®, Pentatomid®, Scutellerid®, etc.
bb. Apex of head directed ventrally, beak arising from the hinder part of the
lower side of the head; sides of face contiguous to the front coxae; first

*Professor C. R. Crosby who has been working upon certain capsids states that he and his
assistant have been bitten by Lygus pratensis, the tarnished plant bug, by Chlamydatus associatus
and by Orthotylus flavosparsus, though without serious results.

Reduviidce of the United States

281

pair of wings, when present, of uniform thickness. Cicadas, scale
insects, plant lice (Aphids), spittle-insects, leaf hoppers, etc .

HOMOPTERA

ReduvtidjE of the United States

(Adapted from a key given by Fracker).

a. Ocelli none; wings and hemelytra always present in the adults; no discodial
areole in the corium near the apex of the clavus. Orthometrops decor ata,

Oncerotrachelus acuminatus, etc., Pennsylvania and south. Sarcince

aa. Ocelli present in the winged individuals; anterior coxae not as long as the
femora.

b. Hemelytra without a quadrangular or discoidal areole in the corium near
the apex of the clavus.

c. Ocelli not farther cephalad than the caudal margins of the eyes; segment
two of the antenna single.

d. Thorax usually constricted caudad of the middle; anterior coxae ex¬
ternally flat or concave . PIRATING

e. Middle tibiae without spongy fossa, head long, no lateral tubercle

on neck. S. stria, Carolina, Ill., Cal . Sirthenia Spinola

ee. Middle tibiae with spongy fossa; fore tibiae convex above; neck
with a small tubercle on each side,

f. Apical portion of anterior tibiae angularly dilated beneath, the

spongy fossa being preceded by a small prominence.

. Melanolestes Stal

g. Black, with piceous legs and antennae. N. E. States (fig. 19a)

. M. picipes

gg. Sides, and sometimes the whole dorsal surface of the abdomen

red. Ill., and southward. M. abdominalis

ff. Tibiae not dilated as in “f”; spongy fossa elongate; metapleural
sulci close to the margin. R. biguttatus (fig. 22). South

. Rasahus A. and S.

dd. Thorax constricted in the middle or cephalad of the middle; anterior
tarsi each three-segmented.

e. Apex of the scutellum narrow, without spines or with a single spine

. REDUVIINjE

f. Antennae inserted in the lateral or dorso-lateral margins of the head;
antenniferous tubercles slightly projecting from the sides of the
head; head produced strongly cephalad; ocelli at least as far
apart as the eyes.

g. Antennae inserted very near the apex of the head; segments
one and three of the beak short, segment two nearly four

times as long as segment one. R. prolixus. W. I .

. Rhodnius Stal

gg. Antennae inserted remote from the vertex of the head.

h. Body slightly hairy; pronotum distinctly constricted; angles
distinct; anterior lobe four-tuberculate, with the middle
tubercles large and conical. M. phyllosoma, large species
the southwest. Meccus Stal

282

Hominoxious Arthropods

hh. Body smooth, margin of the pronotum sinuous, scarcely
constricted; anterior lobe lined with little tubercles
. Conorhinus Lap.

i. Surface of the pronotum and prosternum more or less

grandular.

j. Eyes small, head black; body very narrow, a fifth as

wide as long; beak reaches the middle of the proster¬
num. California . C. protractus

jj. Eyes large, head fuscous; body at least a fourth as wide

as long. Southern species . C. mbro f asciatus

ii. Pronotum and prosternum destitute of granules.

j. Border of abdomen entirely black except for a narrow
yellowish spot at the apex of one segment. Texas

. C. gerstaeckeri

jj. Border of abdomen otherwise marked.

k. Beak slender, joints one and two slightly pilose, two
more than twice as long as one; tubercles at the
apical angles of the pronotum slightly acute, conical.
Md. to Ill. and south. The masked bed bug hunter

(fig. 71) . C. sanguisugus

kk. Beak entirely pilose, joint two a third longer than
joint one; joint one much longer than three;
tubercles at the apical angles of pronotum slightly
elevated, obtuse. Ga., Ill., Tex., Cal. . C. variegatus
ff. Antenna inserted on top of the head between margins, close to the
eyes; antenniferous tubercles not projecting from the side of the
head.

g. Anterior lobe of the pronotum with a bispinous or bituberculate
disc; femora unarmed. S. arizonica, S. bicolor. South¬

western species. Spiniger Burm.

gg. Disc of pronotum unarmed; apex of scutellum produced into
a spine; ocelli close to the eyes; eyes large and close to¬
gether . Reduvius Lamarck

h. Color piceous. Widely distributed' in the United States.

(Fig. 20). R. personatus

hh. More or less testaceous in color. Southwestern states
.R. senilis

ee. Apex of scutellum broad, with two or three spines. . Ectrichodiin.®
f. First segment of the antenna about as long as the head. E. cruciata

Pa. and south; E. cinctiventris, Tex. and Mex .

. Ectrichodia L. et S.

ff. First segment of the antennae short. P. ceneo-nitens. South

. Pothea A. et S.

cc. Ocelli cephalad of the hind margins of the eyes; first segment of the
antennae stout, second segment divided into many smaller segments.
South and west. Homalocoris maculicollis, and Hammatocerus
purcis . HammatoceriNjE

Reduviidce of the United States . 283

bb. Hemelytra with a quadrangular or discoidal areole in the corium near the
apex of the clavus (fig. 159c).

c. Anal areole of the membrane not extending as far proximad as the costal
areole; basal segment of the antenna thickened, porrect; the other
segments slender, folding back beneath the head and the first segment

. Stenopodin\e

d. Head armed with a ramous or furcate spine below each side, caudad
of the eyes.

e. First segment of the antenna thickened, apex produced in a spine
beyond the insertion of the second segment. Species from Va.,

Ill. and south . Pnirontis Stal.

ee. First segment of the antenna not produced beyond the insertion
of the second segment. Pygolampis, N. E. states and south;
Gnathobleda, S. W. and Mex.

dd. Head unarmed below or armed with a simple spine; rarely with a
subfurcate spine at the side of the base. Carolina, Missouri and
south. Slehopoda, Schumannia , Diaditus, Narvesus, Oncocephalus
cc. Anal areole of membrane extending farther proximad than the costal
areole.

d. Ocelli farther apart than the eyes. A. crassipes, widely distributed

in the United States; other species occur in the southwest .

. Apiomerus Hahn.

dd. Ocelli not so far apart as the eyes. Zelin^e

e. Sides of mesosternum without a tubercle or fold in front.

f. Fore femur as long as or longer than the hind femur; first segment
of the beak much shorter than the second. Z. audax, in the
north eastern states; other species south and west. .Zelus Fabr.
ff. Fore femur shorter than the hind femur, rarely of equal length,
in this case the first segment of the beak as long or longer than
the second.

g. First segment of the beak shorter than the second; fore femur
a little shorter than the hind femur; the first segment of the
beak distinctly longer than the head before the eyes. P.
cinctus a widely distributed species (fig. 160). P. punctipes ,

P. spinicollis, Cal., Mex.(= Mityas) Pselliopus Berg.

gg. First segment of the beak as long or longer than the second,

h. Pronotum armed with spines on the disc.

i. Juga distinctly prominent at the apex and often acute or

subacute; fore femur distinctly thickened; hemelytra
usually not reaching the apex of the abdomen. Fitchia
aptera, N. Y., south and west; F. spinosula, South;
Rocconata annulicornis, Texas, etc.

ii. Juga when prominent, obtuse at apex; eyes full width of

the head; fore femur not thickened; pronotum with four
spines on posterior lobe. R. tanrus, Pa., south and west

. Repipta Stal.

hh. Pronotum unarmed on the disc.

284

Hominoxious A rthropods

i. Spines on each apical angle of the penultimate abdominal

segment. A. cinereus, Pa., and south. . Atrachelus A. et S.

ii. Apical angle of the penultimate abdominal segment un¬

armed. Fitchia (in part); Castolus *erox, Arizona,
ee. Sides of the mesosternum with a tubercle of fold in front at the hind
angles of the prosternum; first segment of the beak longer than
the part of the head cephalad of the eyes,
f. Fore femur thickened, densely granulated; hind femur unarmed.

161. Taxonomic details of Diptera. (a) Ventral aspect of abdomen of Cynomyia;

( b ) antenna of Tabanus; (c) ventral aspect of abdomen of Choitophila; (d)
ventral aspect of abdomen of Stomoxys; ( e ) claw of Aedes (Culex) sylves-
tris, male; (f) claw of Hippoboscid; ( g ) foot of dipterous insect showing
empodimm developed pulvllliform; {h) hind tarsal segment of Simulium
vittatum, female; (*) foot of dipterous insect showing bristle-like empodium.

g. Fore tibiae each with three long spines on the ventral side.
S. diadema (fig. I59e), a widely distributed species; and

several southwestern species. Sinea A. et S.

gg. Fore tibiae unarmed. A. multispinosa, widely distributed;

A. tabida, Cal. Acholla Stal.

ff. Fore femur unarmed, rarely a little thickened, a little granulated,
g. Pronotum produced caudad over the scutellum, with a high
mesal tuberculate ridge (fig. 19c). A. cristatus. N. Y. to

Cal. and south.Arilus Hahn.

gg. Caudal lobe of the pronotum six sided, neither elevated nor
produced caudad. H. americanus, Southwest; also several
W. I. and Mexican genera.Harpactor Lap.

Dipt era 285

DIPTERA (Mosquitoes, Midges, Flies)

a. Integument leathery, abdominal segments indistinct; wings often wanting;

parasitic forms.PUPIPARA

b. Head folding back on the dorsum of the thorax; wingless flies parasitic

on bats. Genus Nycteribia . Nycteribiid^:

bb. Head not folding back upon the dorsum of the thorax; flies either winged
or wingless; parasitic on birds and on bats and other mammals,

c. Antennae reduced, wings when present, with distinct parallel veins and
outer crossveins; claws simple; palpi leaf-like, projecting in front of
the head. Flies chiefly found on bats. Several genera occur in North
America . Streblid^e

162. Hippobosca equina, xq. After Osborn.

cc. Antennae more elongate, segments more or less distinctly separated;
head sunk into an emargination of the thorax; wings when present
with the veins crowded toward the anterior margin; palpi not leaf¬
like . HlPPOBOSCIDAs

d. Wings absent or reduced and not adapted for flight.

e. Wings and halteres (balancers) absent. M. ovinus, the sheep tick

. Melophagus Latr.

ee. Wing reduced (or cast off), halteres present.

f. Claw bidentate; ocelli present. On deer after the wings are cast

off. L. depressa . Lipoptena Nitsch

ff. Claw tridentate (fig. 161 f).On Macropis. B. femorata

. Brachypteromyia d Will.

dd. Wings present and adapted for flight,
e. Claws bidentate.

f. Ocelli present; head flat; wings frequently cast off. On birds

before casting of the wing . Lipoptena Nitsch.

ff. Ocelli absent; head round; wings present. The horse tick

H. equina may attack man (fig. 162) . Hippobosca L.

ee. Claws tridentate (fig. 161 f.).
f. Anal cell closed at apical margin by the anal crossvein.

g. Ocelli absent . Stilbometopa Coq.

gg. Ocelli present.

286

Hominoxious Arthropods

h. R4+5 does not form an angle at the crossvein. On birds.
There is a record of one species of this genus attacking man

.Omithomyia Latr.

hh. R4+5 makes an angle at the crossvein. O. confluens.

. Ornithoica Rdi.

ff. Anal cell not closed by an anal crossvein. Lynchia, Pseudolfersia,
and Olfersia are chiefly bird parasites. The first mentioned
genus is said to be the intermediate host of Hcemoproteus columbce.
aa. Abdominal segments chitinous; not parasitic in the adult stage.

b. Antennae with six or more segments and empcdium not developed pulvilli-
form; palpi often with four segments,
c. Ocelli present. Blepharocerid.*, Rhyphid^e, Bibionim:, Myceto-
philid/E, besides some isolated genera of other families,
cc. Ocelli absent.

d. Dorsum of the thorax with a V-shpaed suture; wings usually with
numerous veins; legs often very long and slender. Crane flies.

. TlPULID/E

dd. Dorsum of the thorax without a V-shaped suture.

e. Not more than four longitudinal veins ending in the wing margin;
w T ing usually hairy: antennae slender; coxae not long; tibiae with¬
out spurs, legs long and slender. Small, delicate flies often called

Gall gnats. Cecidomyiid/E

ee. More than four longitudinal veins ending in the wing margin,

f. The costal vein is not produced beyond the tip of the wing; radius
with not more than three branches,

g. Antennae short, composed of ten or eleven closely united seg¬
ments; legs stout; body stout; abdomen oval; anterior
veins stout, posterior ones weak (fig. 163 b); eyes of the male
contiguous over the antennae. Black flies, buffalo flies,

turkey gnats. Many North American species, several of

them notorious for their blood sucking propensities.

.SlMULIIDiE

h. Second joint of the hind tarsus with basal scale-like process and
dorsal excision (fig. 161 h); radial sector not forked; no
small cell at the base of the wing. S. forbesi, jenningsi,
johannseni, meridionale, piscicidium, venustum, vittatum,

etc. Widely distributed species.

.( = Eusimulium) Simulium Latr.

hh. No basal scale-like process on the second joint of the hind
tarsus; radial sector usually forked (fig. 163 b).

i. Face broad, small basal cell of the wing present. P. fulvum,

hirtipes, mutalum, pecuarum, pleurale. . Prosimulium Roub.

ii. Face linear; small basal cell of the wing absent. One

species, P. furc'atum, from California.

. Parasimulium Malloch

gg. Flies of a different structure.

h. Antennas composed of apparently two segments and a terminal
arista formed of a number of closely united segments.
Rare flies with aquatic larvae . Orphnephilid.e

Diptera

287

hh. Antennae of six to fifteen segments, those of the male usually
plumose; legs frequently slender and wings narrow

. CHIRONOMIDiE

i. Media forked (except in the European genus Brachypogon ) ;
thorax without longitudinal fissure and not produced over
the head (except in four exotic genera); antennae usually
fourteen-jointed in both sexes; fore tibia with a simple
comb of setulae, hind tibia with two unequal combs,

middle tibia without comb. CeratopogoniNjE

j. Thorax produced cap-like over the head, wing narrow
and very long. Jenkinsia, Macroptilum and Caly-
ptopogon, eastern hemisphere; Paryplioconiis, Brazil,
jj. Thorax not produced over the head.

k. Eyes pubescent, empodium well developed, or if short
then R2+3 distinct and crossvein-like or the
branches of R coalescent; r-m crossvein present;
fore femora not thickened; wing either with ap-
pressed hairs or with microscopic erect setulae

. Dasyhelea Kieff.

kk. Eyes bare, or otherwise differing from the foregoing.

I . Empodium well developed, nearly as long as the

claws and with long hairs at the base; femora and
fifth tarsal segments unarmed, i.e. without spines
or stout setae; fourth tarsal segment cylindrical,

m. Wing with erect and microscopic setulae. Widely

distributed.

.(= Atrichopogon) Ceratopogon Meig.

mm. Wing with long and depressed hairs. Widely

distributed . Forcipomyia

n. Hind metatarsus shorter or not longer than the
following (i.e. the second tarsal) segment

. Subgenus Prohelea Kieff

nn. Hind metatarsus longer than the following
segment .... Subgenus Forcipomyia Meig.

II . Empodium short, scarcely reaching the middle of

the claws, or vestigial,
m. R-m crossvein wanting.

n. Palpi four segmented; inferior fork of the media

obliterated at the base. Australia .

. Leptoconops Skuse

nn. Palpi three-segmented.

o. Legs spinulose, tarsal claws of the female
with a basal tooth or strong bristle, those
of the male unequal, the anterior with a
long sinuous tooth, the posterior with a

short arcuate tooth. Italy .

. Mycterotypus No£

Horn inoxious A rthropods

oo. Legs unarmed; no crossvein between the
branches of the radius (fig. 163c). New

Mexico . Tersesthes Townsend

mm. R-m crossvein present.

n. Fore femora very much swollen, armed with
spines below, fore tibia arcuate and applied
closely to the inferior margin of the femur,

o. R2+3 present, therefore cell R x and R 2 both
present; wing usually fasciate. United

States. Heteromyia Say.

00. R2+3 not distinct from R4 + 5, hence cell

R3 obliterated. South America.

. Pachyleptus Arrib. (Walker)

nn. Fore femur not distinctly swollen.

o. R 2 + 3 present therefore cells Ri and R 3
both present, or if not, then the branches
of the radius more or less coalescent,
obliterating the cells.

p. At least the tip of the wing with erect
setulae; tip of R4+5 scarcely attaining
the middle of the wing, empodium rather
indistinct, not reaching the middle of the
claws, the claws not toothed, equal, with
long basal bristle; legs without stout

setae. Widely distributed.

.Culicoides Latr.

Haematomyidium and Oecacta are prob¬
able synonyms of this,
pp. Wings bare, if rarely with hair, then the
radius reaches beyond two-thirds the
length of the wing, or the femur or
fifth tarsal segment with stout black
spines.

q. Media unbranched. Europe .

. Brachypogon Kieff

qq. Media branched.

r. Hind femur much swollen and spined.

America and Europe. Serromyia Meg.
rr. Hind femur not distinctly swollen,

s. Cell Rj not longer than high; fork
of the media distad of the cross¬
vein; wing with microscopic setu¬
lae . Stilobezzia Kieff

ss. Cell R r elongate.

t. Femora unarmed. Widely dis¬
tributed. (= Sphaeromias Kieff.

1913 not Curtis?) .

.Johannseniella Will.

Dipt era

289

tt. Femora, at least in part, with
strong black spines. Widely
distributed. Palpomyia Megerle
00. R2+3 coalescent with R4+5 hence cell Ra
is obliterated.

p. In the female the lower branch of the
media with an elbow near its base pro¬
jecting proximad, the petiole of the
media coalescent with the basal section
of the radius, wing long and narrow,
radial sector ending near the tip of the
wing; venation of the male as in Bezzia\

front concave. United States.

. Stenoxenus Coq.

pp. Venation otherwise, front not concave,
q. Subcosta and Ri more or less coalescent
with the costa; wing pointed at the
apex, much longer than the body;
antennas fourteen segmented, not plu¬
mose. India. Haasiella Kieff.

qq. Subcosta and radius distinct from the
costa.

r. Abdomen petiolate... Dibezzia Kieff.
rr. Abdomen not petiolate.

s. Head semi-globose; hind tarsi un¬
usually elongate in the female;
antennas of the male not plumose.

Europe. Macropeza Meigen.

ss. Head not globose, more or less

flattened in front; antennae of
the male plumose. Widely dis¬
tributed . Bezzia Kieff.

t. Fore femora, at least, armed with

stout spines below r .

.Subgenus Bezzia Kieff.

tt. Femora unarmed.

.... Subgenus Probezzia Kieff.
ii. Media of the wing simple, and otherwise not as in “i”. To
this group belong numerous Chironomid genera, none of
which are known to be noxious to man.
ff. The costal vein apparently is continued around the hind margin of
the wing; radius with at least four branches,
g. Wing ovate pointed, with numerous veins; crossveins, if evi¬
dent, before the basal third of the wing; veins very hairy;

very small moth-like flies. PsychodiDjE

h. With elongate biting proboscis; the petiole of the anterior
forked cell of the wing (R 2 ) arises at or beyond the middle of
the wing (fig. 163d).Phlebotomus Rdi.

290

Hominoxious Arthropods

163. Wings of Diptera. (a) Anopheles; ( b) Prosimulium; (c) Johannseniella; (d) Phle-
botomus (After Doerr and Russ); (e) Tersesthes (after Townsend); (/) Ta-
banus; (g) Symphoromyia; (h) Aphiochaeta; (*') Eristalis; (J) Gastrophilus;
( k ) Fannia; ( l) Musca.

Diptera

291

hh. With shorter proboscis; the petiole of the anterior forked

cell arises near the base of the wing .

. Psychoda, Pericoma, etc.

gg. The r-m crossvein placed at or beyond the center of the wing;
wings not folded roof-like over the abdomen,

h. Proboscis short, not adapted for piercing; wings bare (Dixi-
d^e); or wings scaled (CuuciDdE, Subf. CorethriNjE).
hh. Proboscis elongate, adapted for piercing; wings scaled,
fringed on the hind margin; antennas of the male bushy

plumose. Mosquitoes .

.CuliciDjE (exclusive of Corethrix^e)

i. Metanotum without setae.

j. Proboscis strongly decurved; body with broad, ap-
pressed, metalescent scales; cell R 2 less than half as
long as its petiole; claws of female simple, some of the
claws of the male toothed. Several large southern
species believed to feed only on nectar of flowers

. Megarhinus R. D.

jj. Proboscis straight or nearly so, or otherwise different,

k. Scutellum evenly rounded, not lobed; claws simple in
both sexes. Anopheles Meig.

I . Abdomen with clusters of broad outstanding scales

along the sides; outstanding scales on the veins of
the wing rather narrow, lanceolate; upper side of
the thorax and scutellum bearing many appressed
lanceolate scales. Florida and southward (Cellia).

m. Hind feet from the middle of the second segment
largely or wholly snow white,

n. With a black band at the base of the last seg¬
ment of each hind foot .

.A. albimanus* and tarsimaculata*

nn. Without such a band.... A. argyritarsis*
mm. Hind feet black, mottled with whitish and with
bands of the same color at the sutures of the
segments. W. I . A. maculipes

II . Abdomen without such a cluster of scales ; outstand¬

ing scales of the wing veins rather narrow, lanceo¬
late; tarsi wholly black.

m. Deep black, thorax obscurely lined with violace¬
ous, especially posteriorly; head, abdomen and
legs black; no markings on the pleura; ab¬
domen without trace of lighter bandings;
wing scales outstanding, uniform, not forming
spots, though little thicker at the usual points
indicating the spottings. Florida. . A. atropus

*Species marked with an * are known to transmit malaria. Species found only in tropical
North America and not known to carry malaria have been omitted from this table, but all found
in the United States are included.

292

Honiinoxious A rthropods

mm. Otherwise marked when the wings are unspotted,

n. Wings unspotted.

o. Petiole of the first forked cell (R 2 ) more than a
third the length of the cell. Mississippi

valley.A. walkeri

oo. Petiole of the first forked cell a third the

length of the cell. Md . A. barberi

nn. Wings spotted.

o. Front margin of the wings with a patch of
whitish and yellow' scales at a point about
two-thirds or three-fourths of the W’ay from
base to apex of wing.

p. Veins of the wing with many broad obovate
outstanding scales; thorax with a black
dot near the middle of each side. W. I.

.A. grabhami*

pp. The outstanding scales of the wings rather
narrow, lanceolate.

q. Scales of the last vein of the wings white,
those at each end black; R4+5 black
scaled, the extreme apex w'hite scaled.
Widely distributed north and south

(fig. 131 ) .A. punctipennis

A dark variety from Pennsylvania has
been named A. perplexens.
qq. Scales of the last vein of the wing white,
those at its apex black; R4+5 w'hite
scaled and with two patches of
black scales. South and the tropics.
A. franciscanus and pseudopunctipen-
nis*

00. Front margin of the wings wholly black
scaled.

p. Last (anal) vein of the wings white scaled
with three patches of black scales (fig.
132). New r Jersey to Texas. A. crucians*
pp. Last vein of the w'ings wholly black
scaled.

q. Widely distributed north and south

(fig. 130), (= maculipennis) .

. A. quadrimaculatus*

qq. Distributed from Rocky Mountains

westward. A. occidentalis

kk. Scutellum distinctly trilobed.

1 . Cell R 2 less than half as long as its petiole; thorax
with metallic blue scales; median lobe of the
scutellum not tuberculate; few small species which
are not common. Uranotaenia Arrib.

Diptera

293

11. Cell R 2 nearly or quite as long as its petiole, or
otherwise distinct.

m. Femora with erect outstanding scales; occiput
broad and exposed. Large species. P. ciliata.

P. howardi.Psorophora R. D.

mm. Femora without erect scales.

n. Clypeus bearing several scales or hairs, scutel-
lum with broad scales only; back of head
with broad scales; scales along the sides of the
mesonotum narrow; some or the claws
toothed; thorax marked with a pair of
silvery scaled curved stripes; legs black
with white bands at the bases of some of the
segments (fig. 134). Yellow Fever mosquito

.Aedes ( = Stegomyia) calopus.

nn. With another combination of characters.
Numerous species of mosquitoes belonging
to several closely related genera, widely
distributed over the country'. ( Culex , Aedes,
Ochlerotatus, etc.). Culex in the wide sense,
ii. Metanotum with setae. Wyeomyia (found in the United
States); and related tropic genera.

bb. Antennae composed of three segments with a differentiated style or bristle;
third segment sometimes complex or annulate, in which case the empo-
dium is usually developed like the pulvilli, i.e., pad-like (fig. 161 g).

c. Empodium developed pad-like (pulvilliform) i.e., three nearly equal
membranous appendages on the underside of the claws (fig. i6ig).

d. Squamae, head, and eyes large; occiput flattened or concave; third
segment of the antennae with four to eight annuli or segments,
proboscis adapted for piercing; body with fine hairs, never with
bristles; middle tibia with two spurs; wing venation as figured
(fig. i63f); marginal vein encompasses the entire wing. Horse

flies, greenheads, deer flies, gad flies. Tabanid.®*

e. Hind tibia with spurs at tip; ocelli usually present (PANGONIN.*)

f. Third joint of the antennae with seven or eight segments; probo-
cis usually prolonged.

g. Each section the the third antennal segment branched. Central

American species, P. festce . Pityocera G. T.

gg. Sections of the third antennal segment not branched.

h. Upper corner of the eyes in the female terminating in an acute
angle; wings of both sexes dark anteriorly. G. chrysocoma,

a species from the eastern states . Goniops Aid.

hh. Upper comer of the eye in the female not so terminating;
wings nearly uniform in color, or hyaline,

i. Proboscis scarcely extending beyond the palpi; front of the
female wide; much wider below than above. S. W.
States . Apatolestes Will.

*This table to the North American genera of the Tabanidffi is adapted from one given by
M iss Ricardo.

294

Hominoxious Arthropods

ii. Proboscis extending beyond the palpi.

j. Wing with cell M3 closed. Tropic America .

. ( = Diclisa ) Scione Wlk.

jj. Cell M3 open; ocelli present or absent. Two or three
eastern species; many south and west. . Pangonia Rdi.
ff. Third segment of the antenna with five divisions; ocelli present,

g. First and second segments of the antenna short, the second only
half as long as the first, three western species. . . .Silvius Rdi.
gg. First and second segments of the antenna long, the second
distinctly over half as long as the first. Deer flies. Many

species, widely distributed . Chrysops Meig.

ee. Hind tibia without spurs; ocelli absent.

f. Third segment of antenna with four divisions, no tooth or angula¬
tion; wings marked with rings and circles of darker coloring;
front of the female very wide. Widely distributed. H. ameri-

cana, H. punctulata .Hasmatopota Meig.

ff. Third segment of the antenna with five divisions (fig. 161b).

g. Third segment of the antenna not furnished with a tooth or
distinct angular projection.

h. Body covered with metallic scales; front of female of normal
width; front and middle tibiae greatly dilated. L.

lepidota . Lepidoselaga Macq.

hh. Body without metallic scales; antennae not very long, the
third segment not cylindrical, not situated on a projecting
tubercle; front of the female narrow. South. D.

ferrugatus . ( =Diabasis) Diachlorus 0 . S.

gg. Third segment of the antenna furnished with a tooth or a
distinct angular projection.

h. Hind tibiae ciliate with long hairs. S. W. and tropics.

. Snowiella and Stibasoma.

hh. Hind tibiae not ciliate.

i. Species of slender build, usually with a banded thorax and

abdomen; third segment of the antenna slender, the
basal prominence long; wings mostly with brownish
markings. Tropic America . Dichelacera Macq.

ii. Species of a stouter build; third segment of the antenna

stout, its basal process short (fig. 161b). Many species,

widely distributed.Tabanus L.

dd. With another group of characters.

e. Squamae small, antennae variable, thinly pilose or nearly bare species,
without distinct bristles; wing veins not crowded anteriorly, R4 and
R5 both present, basal cells large; middle tibiae at least with spurs

. LEPTIDjE

f. Flagellum of the antenna more or less elongated, composed of

numerous more or less distinct divisions .

. Xylophagin/E and Arthkoceratin.e.

ff. Antennae short, third segment simple, with arista or style; face
small, proboscis short .. Leptin.®

Diptera

295

g. Front tibiae each with one or two spurs, or if absent, then no
discal cell. Triptotricha, Pheneus, Dialysis, Hilarimorpha.
gg. Front tibae without terminal spurs, discal cell present,

h. Hind tibae each with a single spur.

i. Anal cell open (fig. i63g); third antennal segment kidney¬

shaped with dorsal or subdorsal arista; first antennal
segment elongate and thickened. About a dozen species
have been described from the United States, of which at
least one (S. pachyceras) is knowm to be a vicious blood
sucker.Symphoromyia Frauenf.

ii. Anal cell closed; third antennal segment not kidney¬

shaped. Chrysopila, Ptiolina, Spania.

hh. Hind tibiae each with two spurs.

i. Third segment kidney-shaped, the arista subdorsal; anal

cell closed. Atherix Meig.

ii. Third segment of the antenna short and with terminal

arista; anal cell open. Leptis Fabr.

Two European species of this genus have been accused of
blood sucking habits, but the record seems to have
been based upon error in observation.

ee. With another combination of characters .

. Stratiomyiid^e, Cyrtid^e, etc.

cc. Empodium bristlelike or absent.

d. Antennae apparently two-segmented, with three-segmented arista,
wings (rarely wanting) with several stout veins anteriorly, the
weaker ones running obliquely across the wing (fig. 163I1); small,
quick running, bristly, humpbacked flies. Several genera; Aphio-

chaeta, Phora, Trineura, etc. Phorid.®

dd. Flies with other characters.

e. No frontal lunule above the base of the antennae; both R4 and R5
often present; third segment of the antenna often with a terminal
bristle. AsiLlDiE, Mydaid.e, Apiocerid.e, Therevid^e, Sceno-
PIMD.E, Bombyliid/E, Empidid^;, Dolichopodid.e, Lonchop-

TERID.E.

ee. A frontal lunule above the base of the antennae; third segment of the
antenna always simple, i.e., not ringed, usually with a dorsal
arista; R4 and R5 coalesced into a simple vein,

f. A spurious vein or fold between the radius and the media, rarely
absent; the cell R4+5 closed at the apex by vein Mi; few or no
bristles on the body, none on the head; flies frequently with
yellow markings. Eristalis (fig. i63i), Helophilus, and many

other genera . SyrphiDjE

ff. No spurious vein present.

g. Body without bristles; proboscis elongate and slender, often
folding; front of both male and" female broad. . . . Conopid/E
gg. Bristles almost always present on head, thorax, abdomen and
legs.

296

Hominoxious Arthropods

h. Arista terminal; hind metatarsus enlarged, sometimes orna¬
mented, hind tarsus more or less flattened beneath.

. PLATYPEZID®

hh. Flies having a different combination of characters.

i. Head large, eyes occupying nearly the entire head; cell

R 4 -j- s narrowed in the margin; small flies . .Pipunculid/E

ii. Head and eyes not unusually large.

j. Squamae (tegulae, or calyptrae, or alulae) not large, often
quite small, the lower one lacking, or at most barely
projecting from below the upper one (antisquama);
front of both male and female broad, the eyes therefore
widely separated; posthumeral and intraalar macro-
chaeta not simultaneously present; thorax usually
without a complete transverse suture; postalar callus
usually absent; the connectiva adjoining the ventral
sclerites always visible; hypopleural macrochaetae
absent; last section of R4+5 and Mi+o with but few
exceptions nearly parallel; subcostal vein often wanting
or vestigial or closely approximated to Ri; the latter
often short, basal cells small, the posterior ones often
indistinct or wanting; vibrissae present or absent

. Acalyptrate muscoidea

k. Subcosta present, distinctly separated from Ri at the
tip; Ri usually ends distad of the middle of the
wing; the small basal cells of the wing distinct.

I . A bristle (vibrissa) on each side of the face near the

margin of the mouth. Cordylurid®, Sepsid®,
Phycodromid®, Heteroneurid®, Helomyzid®.

II . No vibrissae present.

m. Head nearly spherical, cheeks broad and re¬
treating; proboscis short; the cell R5 closed or
narrowed in the margin; legs very long; tarsi
shorter than the tibiae. Calobata and other

genera . Micropezid®

mm. Flies with another combination of characters.
Rhopalomerid®, Trypetid®, Ortalid®,
SciOMYZin®.

kk. Subcosta absent or vestigial, or if present, then
apparently ending in the costa at the point where
Ri joins it; Ri usually ends in the costa at or before
the middle of the wing.

I . Arista long plumose, or pectinate above; oral vibris¬

sae present; anal cell complete; costa broken at
the apex of Ri. Drosophila, Phortica, and other
genera. Drosophilid®

II . With another combination of characters.

m. The cell M and first M2 not separated by a cross¬
vein; anal cell absent; front bare or only

Diptera

297

bristly above; usually light colored flies.
Hippelates, Oscinus, and other genera. (See

also mmm . Oscinid®

mm. Cell M and cell first M2 often separated by a
crossvein; aijal cell present, complete, though
frequently small; scutellum without spines
or protuberances; oral vibrissae present;
arista bare or short plumose; front bristly at
vertex only; small dark flies. Piophila
(fig. 99), Sepsis and other genera. . . SEPSID®
mmm. The Geomyzid®, Agromyzid®, Psilid®,
Trypetid®, Rhopalomerid®, Borborid®
and Diopsid® differ in various particulars
from either the OSCINID® and the SEPSID®
noted above.

jj. Squamae well developed, usually large, the lower one
frequently projecting from below the upper one; both
posthumeral and intraalar macrochaetae present;
thorax with a complete transverse suture; postalar
callus present and separated by a distinct suture from
the dorsum of the thorax; front of the female broad,
of the male frequently narrow, the eyes then nearly or
quite contiguous; the connectiva adjoining the ventral
sclerites either visible or not; hypopleural macro¬
chaetae present or absent; subcosta always distinct in

its whole course, Ri never short.

.Calyptrate Muscoidea*

k. Oral opening small, mouth parts usually much reduced
or vestigial. This family is undoubtedly of poly-
phyletic origin but for convenience it is here con¬
sidered as a single family. Oestrid® .

1 . The costal vein ends at the tip of R-4+5, Mi+ 2
straight, not reaching the wing margin, hence
cell R5 wide open (fig. i63j); squamae small;
arista bare; ovipositor of the female elongate.
Larvae in the alimentary canal of horses, etc.

. Gastrophilus

m. Posterior crossvein (m-cu) wanting; wings
smoky or with clouds. Europe. G. pecorum
mm. Posterior crossvein (m-cu) present, at least in
part.

*The classification of the Muscoidea as set forth by Schiner and other earlier writers has
long been followed, although it is not satisfactory, being admittedly more or less artificial. With¬
in the last two or three decades several schemes have been advanced, that of Braaer and Bergen-
stamm and of Girschner, with the modifications of Schnabl and Dziedzicki having obtained most
favor in Europe. Townsend, in jqoS, proposed a system which differs from Girschner’s in some
respects, but unfortunately it has not yet been published in sufficient detail to permit us to adopt
it. From considerations of expediency we use here the arrangement given in Aldrich's Cata¬
logue of North American Diptera, though we have drawn very freely upon Girschner's most excel¬
lent paper for taxonomic characters to separate the various groups.

It may sometimes be found that a species does not agree in all the characters with the synop¬
sis; in this case it must be placed in the group with which it has the most characters in common.

298

Hominoxious A rth ropods

n. Wing hyaline with smoky median cross band,
and two or three spots; posterior trochanters
with hook in the male and a prominence in
the female. World wide distribution. G. equi.
nn. Wings without spots.

o. Posterior crossvein (m-cu) distad of the
anterior crossvein (r-m); legs, particularly
the femora, blackish brown. Europe and

North America . G. haemorrhoidalis

00. Posterior crossvein opposite or proximad of
the anterior crossvein. Europe and North

America . G. nasalis

11 . The costal vein ends at the tip of Mi 2, M1+2 with a
bend, the cell R5 hence much narrowed in the
margin, or closed.

m. Proboscis geniculate, inserted in a deep slit;
female without extricate ovipositor; arista
either bare or plumose; squamae large; facial
grooves approximated below,

n. Arista bare, short. Larvae in rodents. Tropic

America. B. princeps . Bogeria Austen

nn. Arista pectinate above.

o. Tarsi broadened and flattened, hairy, anal
lobe of the wing large. Larvae in rodents.
A number of American species. Cuterebra.
00. Tarsi slender, not hairy; anal lobe of the
wing moderate. Larvae in man and other
mammals. Tropic America. D.cyaniven-

tris.Dermatobia Br.

mm. Mouth parts very small, vestigial; arista bare,
n. Facial grooves approximated below, leaving a
narrow median depression or groove,
o. Cell R5 closed and petiolate, body nearly
bare. Larvae in the nasal cavities of the
smaller Ungulates. The sheep bot fly.
O. ovis. Widely distributed. Oestrus L.
00. Cell R5 narrowly open, body hairy. Larvae
parasitic on deer. Europe and America

. Ceplienomyia Latr.

nn. Facial grooves far apart, enclosing between
them a broad shield-shaped surface; squamae
large; female with elongate ovipositor.

Larvae hypodermatic on Ungulates.

. Hypoderma Clark

o. Palpi wanting; tibiae thickened in the middle,

p. Hair at apex of the abdomen yellow; legs
including femora yellowish brown....

H. diana

Dipt era

299

pp. Hair at the apex of the abdomen reddish
yellow. Europe and America,
q. Tibiae and tarsi yellow; femora black

. H. lineata

qq. Legs black with black hair; tips of
hind tibia and tarsi yellowish brown

. H. bovis

00. Palpi small, globular; tibiae cylindrical,

straight. On reindeer. O. tarandi

. Oedemagena Latr.

kk. Oral opening of the usual size; mouth parts not
vestigial.

1 . Hvpopleurals wanting; if three sternopleurals are
present the arrangement is 1:2; conjunctiva
(fig. 161 c) of the venter usually present; if the
terminal section of M1+2 is bent it has neither fold
nor appendage (AnthomyiiDjE of Girschner).

m. Sternopleurals wanting; M1+2 straight toward
the apex, costa ends at or slightly beyond the

tip of R4+5; mouth parts vestigial .

. GASTR0PHILIN>E. See OESTRIDiE

mm. Sternopleurals present, if rarely absent then
differing in other characters,

n. Caudal margin of the fifth ventral abdominal
sclerite of the male deeply notched on the
median line usually to beyond the middle;
abdomen often cylindrical or linear; abdomen
often with four to eight spots; eyes of the
male usually widely separated; stemo-
pleurals three, arranged in an equilateral
triangle; subapical seta of the hind tibia
placed very low; M1+2 straight; anal vein
abbreviated; wings not rilled. Ccenosia,
Caricea, Dexiopsis, Hoplogaster, Schceno-

myia, etc. (Ccenosin/e)* .

. Anthomyiid.-e in part

nn. Caudal margin of the fifth ventral abdominal
sclerite of the male incurved, rarely deeply
cleft, rarely entire, in a few' genera
deeply two or three notched; M1+2 straight

♦There are several genera of flies of the family Cordylurida (i.e. Acalyptratce ) which might be
placed with the Anlhomyiida (i.e. Calyptrala ), owing to the relatively large size of their squamae.
As there is no single character which will satisfactorily separate all doubtful genera of these two
groups we must arbitrarily fix the limits. In general those forms on the border line having a
costal spine, or lower squama larger than the upper, or the lower surface of the scutellum more
or less pubescent, or the eyes of the male nearly or quite contiguous, or the eyes hairy, or the
frontal setae decussate in the female; or any combination of these characters may at once be
placed with the Anthomyiida. Those forms which lack these characteristics and have at least
six abdominal segments (the first and second segments usually being more or less coalescent)
are placed with the Acalyptrates. There are other acalyptrates with squamae of moderate size
which have either no vibrissae, or have the subcosta either wholly lacking or coalescent in large
part with R,, or have spotted wings; they, therefore will not be confused with the calyptrates.

3 °°

Hominoxious Arthropods

or curved; abdomen usually short or elongate
oval; sternopleurals, if three are present,
arranged in the order 1:2 ina right triangle.
.... (MusciNjE-Anthomyiin.® of Girschner)

o. M]-j-2 straight, hence cell R5 not narrowed in

the margin . AnthomytiDjE in part

p. Underside of the scutellum more or less
sparsely covered with fine hairs; anal
vein nearly ahvays reaches the hind
margin of the wing; extensor surface of
the hind tibiae with a number of stout
setae; squamae often small and equal.
Anthomyia, Chortophila, Eustalomyia,
Hammomyia, Hylemyia, Prosalpia, Pego-
myia, etc. . . . HylemyiNjE-Pegomyin.®
pp. Underside of the scutellum bare; anal
vein does not reach the wing margin,

q. First anal vein short, second anal sud¬
denly flexed upwards; hind tibiae each
with one or two strong setae on the
extensor surface. Fannia ( = Homalo-
myia), Ccelomyia, Choristoma, Eur-
yomma, Azelia, etc. FANNIN.E-AZELIN.E
qq. Anal veins parallel or divergent.

r. Setae on the exterior surface of the hind
tibiae wanting (except in Limnaricia
and Ccenosites), lower squama not
broadened to the margin of the
scutellum. Leucomelina, Limno-
phora, Limnospila, Lispa, Mydaea,

Spilogaster, etc.

. MYD.EIN/E-LIMNOPHORIN.E

rr. One (rarely more) seta on the extensor
surface of the hind tibia; squamae
usually large and unequal. Hydro-
taea, Aricia, Drymeia, Ophyra,
Phaonia (= Hyetodesia ), Pogono-
myia, Trichophthicus, etc. Aricine
00. M1+2 curved or bent, hence the cell R5 more
or less narrowed in the margin.
(MusciNiE). MusciDiE in part. See
page 303 for generic synopsis.

11 . Hypopleurals present; when three sternopleurals
are present the arrangement is 2:1 or 1 : 1 : 1 .

. (Tachinid^e of Girschner)

m. Conjunctiva of the ventral sclerites of the ab¬
domen present, frequently well developed,
surrounding the sclerites.

Diptera

3 QI

n. Mouth parts vestigial. Oestrid^e. See page
297 for generic synopsis,
nn. Mouth parts well developed.

o. M1+2 straight, hence cell R& wide open in
the margin; costa ending at the tip of R5;
three stemopleurals present; antennal
arista plumose. Syllegoptera. Europe.
.... (Syllegopteriis) . . Dexiid.e in part
00. M1+2 bent, hence cell R5 narrowed in the
margin; stemopleurals rarely wanting,
usually 1 :i or 0:1; facial plate strongly
produced below vibrissal angle like the
bridge of the nose; antennal arista bare.
Parasitic on Hemiptera and Coleoptera.
Allophora, Cistogaster, Clytia, Pliasia,
etc. (Phasiin/e) . .Tachinid^e in part,
mm. Conjunctiva of the ventral sclerites invisible
(fig. 161a).

n. Second ventral sclerite of the abdomen lying
with its edges either upon or in contact with
the ventral edges of the corresponding
dorsal sclerite.

o. Outermost posthumeral almost always lower
(more ventrad) in position than the pre-
sutural macrochaeta; fifth ventral abdomi¬
nal sclerite of the male cleft beyond the
middle, often strongly developed; body
color very frequently metallic green or
blue, or yellow; arista plumose. (CALLI-

phorin.*).MusciDjE in part.

See page 303 for generic synopsis.

00. Outermost posthumeral macrochaeta on
level or higher (more dorsad) than the
presutural macrochaeta; arista bare, pube¬
scent, or plumose only on the basal two-
thirds; body coloring usually grayish

(fig. 106) . SARCOPHAGIDiE

p. Fifth ventral sclerite of the male either
wanting or with the caudal margin
straight; presutural intraalar rarely

present . (Sarcophagus)

q. Fifth ventral abdominal sclerite of the
male much reduced, the remaining
segments with straight posterior mar¬
gin, overlapping scale-like; in the
female only segment one and two scale¬
like, the others wholly or in part
covered; stemopleurals usually three
or more. Sarcophaga and related
genera.

302

Hominoxious Arthropods

qq. Fifth ventral sclerite of the male plainly
visible; sternopleurals usually two.
Sarcophila, Wohlfahrtia, Brachycoma,
Hilarella, Millogramma, Metopia,
Macronychia,, Nyctia, Paramacrony-
chia, Pachyphthalmus, etc.
pp. Fifth ventral abdominal sclerite of the
male cleft to beyond the middle; ventral
sclerites usually visible, shield-like.
Rhinophora, Phyto, Melanophora. . . .
. Rhinophorin/e

164. Glossina palpalis. (X 4 .) After Austen.

nn. Second ventral abdominal sclerite as well as
the others more or less covered, sometimes
wholly, by the edges of the dorsal sclerite.
o. The presutural intraalar wanting; ventral
sclerites two to five nearly or quite covered
by the edges of the corresponding dorsal
sclerites; base of the antenna) usually at or
below the middle of the eye; arista usually
plumose; legs usually elongate; abdomi¬
nal segments with marginal and often

discal macrocha;tae. Dexiidaj

00. Presutural intraalar present, if absent, then
the ventral sclerites broadly exposed
or the fifth ventral sclerite vestigial;

Muscidaz

303

base of the antennae usually above the
middle of the eye; arista bare; at least
two posthumerals and three posterior
intraalars present. Parasitic on cater¬
pillars, etc. Tachinid^e

SYNOPSIS OF THE PRINCIPAL GENERA OF THE MUSCID.® OF THE WORLD

. Proboscis long, directed forward, adapted for piercing, or oral margin much
produced, snout-like.

b. Oral margin produced snout-like; vibrissa placed high above the oral
margin; antennal arista either pectinate or more or less plumose,

c. Antennal arista short or long-plumose; neither sex with distinct

orbital bristles.

d. No facial carina between the antennae . Rhynchomyiin.e

e. Arista short-plumose. R.speciosa. Europe .... Rhynchomyia R. D.
ee. Arista long-plumose. I. phasina. Europe and Egypt. Idiopsis. B.B.
dd. With flattened carina, the bases of the antennae separated; no abdom¬
inal macrochaetae . Cosminin^e

C. fuscipennis. South Africa . Cosmina

cc. Antennal arista pectinate; bases of the antennae separated by a flat¬
tened carina . Rhiniinve R. D.

d. Cell R5 open, or closed at the margin.

e. Third segment of the antenna twice as long as the second; claws of
both sexes short; cell R5 open. I. lunata. Eastern Hemisphere.

. Idia Meigen

ee. Third segment of the antenna three times as long as the second;
cell R5 open or closed; claws of the male long and slender, of the
female shorter than the last tarsal joint. I. mandarina, China.

. Idiella B. B.

dd. Cell R5 petiolate. Rhinia; and Beccarimyia Rdi.

bb. Proboscis long, directed forward, adapted for piercing. STOMOXIN^E

c. Arista flat, pectinate above with plumose rays; sternopleurals 1:2;
bases of the veins Ri and R4+5 without setae; base of the media bowed
down; apical cell opens before the apex of the wing. African species

. Glossina Wied.

d. Species measuring overtw r elve mm. in length. G. longipennis and fusca.
dd. Species less than twelve mm. in length,

e. All segments of the hind tarsi black.

f. The fourth and fifth segments of the fore tarsi black; antennae

black (fig. 164) . G. palpalis R. D.

ff. Otherwise marked. G. bocagei, tachinoides, pallicera.

ee. First three segments of the hind tarsi are yellow, the fourth and
fifth segments are black.

f. Fourth and fifth segments of the first and second pair of tarsi are
black.

g. The yellow bands of the abdominal segments occupy a third of

the segment (fig. 165). G. morsitans Westw.

gg. The yellow band on each segment of the abdomen occupies a
sixth of the segment. G. longipalpis Wied.

304 Hominoxious Arthropods

ff. Tarsi of the first and second pairs of legs wholly yellow.

. G. pallidipes Austen

cc. Rays of the arista not plumose; only one or two stemopleurals; base of
the media not strongly bowed down; apical cell opens at or very near
the apex of the wing.

d. Vein R4+5 without setae at the base; palpi about as long as the pro¬
boscis.

e. Arista pectinate (i. e. rays on one side only), the rays often undulate;
two yellow stemopleurals often difficult to detect; vein M 1-1-2
only slightly bent, the apical cell hence wide open. The horn fly,
H. irritans ( = Lyperosia serrata) and related species. Widely dis¬
tributed (figs. 167, 168).Haematobia R. D. not B. B.

165. Glossina morsitans. (X 4 .) After Austen.

ee. Arista also with rays below; vein M1+2 more strongly bent, the
apical cell hence less widely open.

f. Palpi strongly spatulate at the tips, lower rays of the arista about

six in number, B. sanguinolentus. South Asia.

. Bdellolarynx Austen

ff. Palpi feebly spatulate; apical cell of the wing narrowly open
slightly before the tip; stemopleurals black, anterior bristle

sometimes absent. H. atripalpis. Europe.

. Haematobosca Bezzi

dd. Vein R4A5 with setae at the base.*

*Pachymyia Macq. is closely related to Stomoxys. It differs in having the arista rayed both
above and below. P. vexans, Brazil.

Muse idee

305

e. Veins Ri and R.j-j-5 with setae at the base; two equally prominent
stemopleural macrochaetae; arista with rays both above and be¬
low; palpi as long as the proboscis; apical cell of the wing wide

open. L. tibialis. ( Hcematobia B. B. not R. D.) .

. Lyperosiops Town.

ee. Only vein R4+5 with basal setae; anterior stemopleural macro-
chaeta wanting; arista pectinate.

f. Palpi as long as the proboscis, the latter stout, with fleshy termi¬
nal labellae; apical cell narrowly open; stemopleural macro¬
chaetae black. S. maculosa from Africa and related species

from Asia. Stygeromyia Austen

ff. Palpi much shorter than the proboscis, the latter pointed at the
apex, without fleshy labellae; apical cell of the wing wide open.
S. calcitrans, the stable fly and related species. Widely dis¬
tributed in both hemispheres (fig. no). Stomoxys Geof.

aa. Proboscis neither slender nor elongate, the labellae fleshy and not adapted for
piercing.

b. Hypopleurae without a vertical row of macrochaetae.MUSCIN^E

c. Arista bare; distal portion of R4+5 broadly curved at the end; hypop-
pleurae with a sparse cluster of fine hairs. S. braziliana, Southern

States and southward . Synthesiomyia B. B.

cc. Arista pectinate or plumose.

d. Arista pectinate. H. vittigera, with the posterior half of the abdomen

metallic blue. Mexico. Hemichlora V. d. W.

dd. Arista plumose.

e. Middle tibia with one or more prominent setae on the inner (flexor)
surface beyond the middle, or inner surface very hairy,

f. Ri ends distad of the m-cu crossvein; R4+5 with a broad curve
near its apical end. (= Neomesembrina Schnabl, = Metamesem-
brina Town). M. meridiana. Europe. . . . Mesembrina Meigen
ff. Ri ends proximad of the m-cu crossvein.

g. Eyes pilose, sometimes sparsely in the female.

h. Female with two or three stout orbital setae; the hind metatar¬
sus of the male thickened below 7 at the base and penicillate.

D. pratorum. Europe. Dasyphora R. D.*

hh. Neither sex with orbital setae.

i. Abdomen without macrochaetae; arista plumose. C.

asiatica. Eastern Hemisphere... Cryptolucilia B. B.

ii. Abdomen with strong macrochaetae; arista very short-

plumose, nearly bare. B. tachinina. Brazil .

. Reinwardlia B. B.

gg. Eyes bare.

h. Body densely pilose; thoracic macrochaetae wanting; middle
tibiae much elongate and bent; last section of R4+5 with a
gentle curve. H. ( Mesembrina ) mystacea, el al., Europe
and H. solilaria, N. America . . . Hypodermodes Town,
hh. Body not densely pilose.

♦The genus Eudasyphora Town, has recently been erected to contain D. lasiophthalma.

3°6

Hominoxious Arthropods

i. Dorsocentrals six; last section of R4+5 with a gentle curve,
j. Inner dorsocentrals (“acrostichals”) wanting; sterno-

pleurals arranged 1:3. P. cyanicolor, cadaverina, etc.

Europe and America. Pyrellia R. D.

jj. Inner dorsocentrals (“acrostichals”) present; stemo-
pleurals arranged 1:2. E. latreillii. North America.
. Eumesembrina Town.

ii. Dorsocentrals five; inner dorsocentrals present; last

section of R4+5 with a rounded angle; stemopleurals
arranged 1:2. P. cornicina Europe and America.

{Pseudopyrellia Girsch.). Orthellia R. D.

ee. Middle tibia without a prominent bristle on the inner surface beyond
the middle.

166. Pycnosoma marginale. (X4.) After Graham-Smith.

f. Squamula thoracalis broadened mesad and caudad as far as the
scutellum.

g. Stemopleural macrochsetae arranged in an equilateral triangle;
front of both sexes broad; gense bare; dorsocentrals six,
small; wing not rilled. (To Coenosin.®). Atherigona Rdi.
gg. Stemopleural macrochaetae when three are present, arranged
in a right triangle.

h. Last section of R44-5 with a more or less rounded angle
(fig. 163I).

i. Eyes of the male pilose or pubescent, of the female nearly

bare; m-cu crossvein usually at or proximad of the mid¬
distance between the r-m crossvein and the bend of

R4+5. P. (= Placomyia R. D.) vitripennis .

.. Plaxemyia R. D.

ii. Eyes bare; the m-cu crossvein always nearer to the bend of

R4-I-5 than to the r-m crossvein,

j. Apex of the proboscis when extended reveals a circlet of
stout chitinous teeth. P. insignis Austen, of India,
bites both man and animals. (= Pristirhynchomyia)
. Philaematomyia Austen

Muscidaz

3°7

jj. Apex of the proboscis without black teeth.

k. Eyes of male separated by a distance equal to a fourth
the width of the head. House or typhoid fly.
M. domestica L. Widely distributed.. Musca L.
kk. Eyes of the male contiguous. E. corvina. Europe.

.Eumusca Town

hh. Last section of R4+5 with a gentle curve (fig. 102).

i. Eyes pilose.

j. Claws in the male somewhat elongated; no orbitals in
either sex; antennas separated at the base by a flat
carina; abdomen marked with red or yellow. G.
maculata. Europe and America... .Graphomyia R. D.
jj. Claws short and equal in the two sexes; two or three
stout orbital macrochaetae in the female; Rj scarcely
produced beyond the r-m crossvein; eyes contiguous
in the male. P. obsoleta. Brazil . . Phasiophana Br.

ii. Eyes bare; fronto-orbital macrochaetae in a double row,

antennae contiguous at the base,
j. One or more pairs of well developed anterior inner dorso-
central (acrostichal) macrochaetae; seta on extensor
surface of hind tibia. M. assimilis, stabulans, etc.

Europe and America.Muscina R. D.

jj. Anterior inner dorsocentrals and the setae on the ex¬
tensor surface of the hind tibia wanting. M. micans,
etc. Europe and North America. . . .Morellia R. D.
ff. Squamula thoracalis not broadened mesad and caudad, not
reaching the margin of the scutellum; macrochaetae on extensor
surface of the hind tibia wanting,
g. Eyes pubescent. M. meditabunda. Europe and America.

. Myiospila Rdi.

gg. Eyes bare; Ri ends before the middle of the wing. A number

of species from the tropics of both hemispheres.

. Clinopera V. d. W.

bb. Hypopleurae with a vertical row of macrochaetae.

c. Eyes pubescent.

d. Rj ends about opposite the r-m crossvein; basal section of R4+5 bristly
nearly to the crossvein; S. enigmatica. Africa. Somalia Hough
dd. Ri ends distad of the r-m crossvein.

e. Eastern hemisphere. Australasia. N. ochracea, dasypthalma.

. Neocalliphora Br.

ee. Western Hemisphere. T. muscinum. Mexico. . Tyreomma V. d. W.
cc. Eyes bare.

d. The vibrissal angle situated at a noticeable distance above the level of
the margin of the mouth.

e. Sternopleural macrochaetae arranged in the order 1:1.

f. Genae with microchaetae.

g. Body grayish, with depressed yellow woolly hair among the
macrochaetae; wings folded longitudinally over the body when

3°8

Hominoxious Arthropods

at rest. Cluster flies. P. rudis and related species, widely

distributed . Pollenia R. D.*

gg. Body metallic blue or green. Eastern Hemisphere.

h. Vibrissal angle placed very high above the oral margin; a
carina between the antenna*; outer posthumeral wanting;

anterior intraalar present. T. viridaurea. Java .

. Thelychceta Br.

167. Horn fly. (a) egg; (2>) larva; (c) puparium; ( d ) adult. (X4). Bureau of Entomology

hh. Vibrissal angle moderately high above the oral margin;
carina small or wanting; no post humeral macrochaeta;
lower squama hairy above. ( = Paracompsomyia

Hough) (fig. 166) . Pycnosoma Br.

ff. Gena bare. S. terminata. Eastern Hemisphere .

. Strongyloneura Bigot

ee. Stemopleurals arranged 2:1.

f. Body metallic green or blue, with gray stripes; gena hairy to the
lower margin; post humerals often wanting; lower squama bare

above. ( = Compsomyia Rdi.) . Chrysomyia R. D.

g. With one or two orbitals; height of bucca less than half the

height of the eye. South and east U. S. (fig. 107) .

. C. marcellaria

gg. No orbitals; height of bucca about a third less than height of
eye. West U. S . C. wheeler i Hough

*Nitellia, usually included in this genus has the apical cell petiolate. A pollenia Bezzi, has
recently been separated from Pollenia to contain the species P. nudiuscula. Both genera belong
to the Eastern hemisphere.

Muscidce

3°9

ff. Body black or sordidly metallic greenish gray, usually yellow pol-
linose or variegate; genae at most hairy above. N. slygia.

Eastern Hemisphere. Neopollenia Br.

dd. Vibrissal angle situated nearly on a level of the oral margin,

e. Species wholly blackish, bluish, or greenish metallic in color.

f. First section of R4+5 with at most three or four small bristles at
the immediate base.

g. The bend of R4+5 a gentle curve; costal spine present; cell R5
closed, ending before the apex of the wing. 5 . cuprina.

Java. Synamphoneura Bigot

gg. Bend of R4+5 angular; or the insect differs in other characters ;
dorsal surface of the squamula thoracalis hairy (except in
Melinda)-, arista plumose only on the basal two-thirds
(except usually in Calliphora and Eucalliphora).

1G8. Head of horn-fly (Lyperosia irritans); (a) female; (6) male; (c) lateral aspect of female.

h. Arista plumose only on the basal two-thirds.

i. Base of the antennae ventrad of the middle of the eye; eyes
of the male nearly contiguous; genae hairy; second
abdominal segment with median marginal macrochaetae;
two, rarely three, postsutural intraalar macrochaetae.

j. Squamula thoracalis dorsally with long black hairs; male
hypopgium two-segmented, large, projecting; claws
and pullvilli of the male elongate; three strong stemo-
pleural macrochaetae; genae at least half the width of the
eye; buccae (cheeks) half the height of the eyes; ovivi-

parous. 0 . sepulcralis. Europe . Onesia R. D.

jj. Dorsal surface of the squamula thoracalis bare; male
hypopygium small, scarcely projecting below; claws
and pulvilli not elongate; two stout stemopleural
macrochaetae, sometimes with a delicate one below the
anterior; genae nearly linear in the male ; buccae about
a third of the eye height; oviparous. M. ccerulea.
Europe. Melinda. R. D.

3 IO

Hominoxious Arthropods

169. Lateral and dorsal aspects of the thorax, and frontal aspect of the head of a muscoidean
fly, with designations of the parts commonly used in taxonomic work.

Muscidce

3ii

ii. Base of the antennae dorsad of the middle of the eye; eyes
of both sexes distinctly separated; dorsal surface of
the squamula thoracalis with black hairs; two post
sutural intraalar macrochaetae.
j. Hypopygium of the male large, with a pair of slightly
curved forceps whose ends are concealed in a longi¬
tudinal slit in the fifth ventral sclerite; third posterior
inner dorso-central (acrostichal) macrochaetae absent;
anterior intraalar rarely present; abdomen usually not
pollinose; the second segment without median marginal
macrochaetae; face yellow. C. mortuorum, cadaverina,
and related species. Both hemispheres.

170. Sepsis violacea; puparium and adult. (See page 297 .) After Howard.

jj. Three pairs of posterior inner dorsocentrals (acrostichals)
present; second abdominal segment with a row of
marginal macrochaetae; genae hairy, at least above,
k. Hypopygium of the male with a projecting style.
5 . stylifera. Europe. Steringomyia Pok.

*The following three genera are not sufficiently well defined to place in this synopsis. In
color and structural characters they are closely related to Cynomyia from which they may be
distinguished as follows. Calapicephala Macq., represented by the species C. splendens from
Java, has the setae on the facial ridges rising to the base of the antennae and has median margi¬
nal macrochaetae on the abdominal segments two to four: Blepharicnema Macq., represented by
B. splendens from Venezuela has bare genae, oral setae not ascending; tibiae villose; claws short
in both seses; Sar'onesia Bigot with the species -S', chlorogaster from Chile, setose genae; legs
slender, not villose; claws of the mae! elongate.

312

Hominoxious A r thro pods

kk. Hypopygium of the male without style. A. stelviana

B. B . Acrophaga B. B.

hh. Arista usually plumose nearly to the tip; posterior dorso-
centrals and inner dorsocentrals (acrostichals) well
developed; dorsal surface of the squamula thoracalis
hairy; abdomen metallic and usually pollinose; genae
hairy.

i. With one pair of ocellar macrochaetae. C. vomitoria,

erythrocephala, viridescens, and related species. Both
hemispheres . Calliphora R. D.

ii. With two strong pairs of ocellar macrochaetae. .E. latifrons.

Pacific slope of the U. S . Eucalliphora Town.

ff. First section of R4+5 bristly near or quite half way to the small
crossvein; dorsal surface of the squamula thoracalis is bare;
the hypopygium of the male is inconspicuous,

g. Genae bare; posterior inner and outer dorsocentrals distinct
and well developed. L. ccesar, sericata, sylvarum, and
related species. Widely distributed in both hemispheres

(fig. 103).Lucilia R. D.

gg. Genae with microchaetae, at least down to the level of the base
of the arista.

h. Mesonotum flattened behind the transverse suture.

i. Posterior dorsocentrals inconstant and unequally developed;

one pair of posterior inner dorsocentrals. P. terraenova.
North America. Protophormia Town.

ii. Posterior dorsocentrals well developed, the inner dorso¬

centrals (acrostichals) unequally developed. P. azurea,

chrysorrhcea, etc. Europe and America .

. Protocalliphora Hough

hh. Mesonotum not flattened behind the transverse suture;
posterior inner and outer dorsocentrals inconstant
and unequally developed. P. regina. Europe and

America . Phormia R. D.

ee. Species more or less rufous or yellow in color.

f. Anterior dorsocentrals wanting; first section of the R4+5 at most
only bristly at the base, bend near apex rectangular, Ri ends over
the crossvein; fronto-orbital macrochaeta absent; eyes of the
male contiguous. C. semiviridis. Mexico . . Chloroprocta V. d. W
ff. With another combination of characters.

g. Body robust, of large size, abdomen elongate, not round; genae
with several ranges of microchaetae; vibrissal ridges strongly
convergent; abdomen with well developed macrochaetae;
costal spine usually absent; eyes of the male widely separated,

h. Peristome broad, pteropleural macrochaetae distinct; one or
two sternopleurals; in the female a single orbital macro¬
chaeta; last abdominal segment without discal macro¬
chaetae; hypopygial processes of the male with a long
stylet; second abdominal segment of the female sometimes

171. Stigmata of the larvae of Muscoidea. Third instar. (a) Cynomyia cadavarina; ( 6 ) Phormia regina; (c) Chrysomyia macel-
laria; (d) Musca domestica; (e) Sarcophaga sp ; (/) Oestris ovis; ( g ) Gastrophilus equi; ( h) Sarcophaga sp; (»') Pegomyia
vicina; (j) Protocalliphora azurea; (k) Hypoderma lineata; ( l ) Muscina stabulans. Magnification for f, g, and k. x 25 ;
all others, x 50 .

Muscidos

313

3i4

Hominoxious Arthropods

much elongate. A. luteola (fig. 86). Africa. The sub¬
genus Cheeromyia Roub. is included here. Auchmeromyia B.B.
hh. Peristome narrow; no pteropleurals, two sternopleurals;
two orbitals in the female; second segment not elongate;
the fourth with two well developed discal macrochaetae.

B. depressa. Africa.Bengalia R. D

gg. With another combination of characters.

h. Costal spine present; body in part black; antennas notice¬
ably shorter than the epistome, inserted above the middle
of the eye and separated from each other by a carina;
abdominal segments with marginal macrochaetas; stemo-

pleurals 2:1 or 1:1. Paratricyclea Villen.

hh. Costal spine not distinct, or if present, insect otherwise
different.

i. Genae with several ranges of microchaetae; vibrissal ridges

strongly converging; peristome broad; arista moderately
plumose; sternopleurals usually 1:1; color entirely

testaceous. C. anthropophaga (fig. 87) and grunbergi.

Africa.Cordylobia Grunb.

ii. Genae bare or with but one range of setae; vibrissal ridges

less converging; peristome narrow; arista long plumose,

j. Genas with a single row of microchaetae.

k. Sternopleurals 2:1; color entirely testaceous.

. Ochromyia Macq. *

kk. Sternopleurals l:l. P. varia Hough. Africa.

. Parochromyia Hough

jj. Genae bare.

k. Basal section of R4+5 bristly only at the immediate
base, distal section with a broad curve; distal

portion of the abdomen metallic; sternopleurals

usually 1:1. rarely 2:1. M. ceneiventris Wd. Tropic

America. Mesembrinella. G. T.

kk. R4+5 bristly at least nearly half way to the small
crossvein; sternopleurals 1:1.

I . Macrochaetas of the abdomen marginal; neither sex

with orbitals; no carina between the base of the
antennae; three pairs of presutural inner dorso-
centrals. Eastern hemisphere. T. ferruginea.
Tricyclea V. d. W. ( = Zonochroa B. B. according
to Villeneuve 1914).

II . Abdomen without macrochaetas; wing usually with

a marginal streak and gray markings. Brazil
. Hemilucilia B. B.

*Plinlhomyia Rdi. and Hemigymnochiita Corti are related to Ocliromyia, though too briefly
described to place in the key.

Muscoidea

3i5

median line is indicated in each figure.

Si6

Homi-noxious Arthropods

SIPHONAPTERA. Fleas
Adapted from a table published by Oudemans.

a. Elongated fleas, with jointed (articulated) head, with combs (ctenidia) on
head and thorax; with long, oval, free-jointed flagellum of the antenna

(fig. 92d).Suborder FRACTICIPATA

b. With ctenidia in front of the antennae and on the genae (cheeks); maxillae
with acute apices; labial palpi five-segmented, symmetrical; eyes poorly

developed or wanting. On rodents. Hystrichopsyllid.e

c. Abdominal segments without ctenidia.

d. Post-tibial spines in pairs and not in a very close set row; head with

ctenidia. Ctenophthalmus Kol.

dd. Post-tibial spines mostly single and in a close set row. Ctenopsyllus
and Leptopsyllus. The last genus has recently been erected for
L. musculi, a widely distributed species occurring on rats and mice,
cc. Abdominal segments with one or more ctenidia; post-tibial spines in
numerous, short, close-set transverse rows on posterior border with
about four spines in each row. H. americana. . Hystrichopsylla Taschenb.
bb. With only two pairs of subfrontal ctenidia; labial palpi five-segmented,
symmetrical; eyes vestigial or wanting. On bats. ( = Ischnopsyl-

lid,e) . Nycteridipsyllid.e

With more or less blunt maxilla; all tibiae with notch; a single antepygi-
dial bristle; metepimeron without ctenidium. N. crosbyi from
Missouri was found on bats. Rothschild suggests that this is probably
the same as N. insignis.

.( = Ischnopsyllus = Ceratopsyllus), Nycteridiphilus

aa. Head not jointed, i.e. the segments coalescent, traces of the segmentation
still being visible in the presence of the vertex tubercle, the falx (sickle¬
shaped process), and a suture.Suborder INTEGRICIPITA

b. Flagellum of the antennas long and oval.

c. Usually elongate fleas, with a free-segmented flagellum of the antenna;
thorax not shorter than the head, longer than the first tergite.

d. Genre of the head and the pronotum with ctenidia. . . . Neopsyllid.e

e. Labial palpi four or five-segmented; symmetrical; hind coxae with
patch of spines inside; row of six spatulate spines on each side in
front of the antennas. C. ornata found on a California mole

. Corypsylla

ee. Labial palpi two-segmented, transparent, membranous. On

hares . Spilopsyllus Baker

dd. No ctenidium on the head.

e. Pronotum with ctenidium . Dolichopsyllid^e

f. Labial palpi five-segmented, symmetrical.

g. Antepygidial bristles one to three; eyes present.

h. Inner side of hind coxae distally with a comb of minute teeth;

falx present. On rodents and carnivores .

. Odontopsyllus Baker

hh. Inner side of hind coxae without comb or teeth. Many

North American species on rodents.

. Ceratophyllus Curtis

Siphonaptera

3 T 7

gg. Antepygidial bristles five on each side; eyes absent; suture

white. D. stylosus on rodents. Dolichopsyllus Baker

ff. Labial palpi four or five-segmented; asymmetrical (membranous
behind), apex acute. Hoplopsyllus anomalus found on Spermo-

philes in Colorado . Hoplopsyllid^e

ee. Pronotum without ctenidium. Anomiopsyllus californicus and

nudatus on rodents . Anomiopsyllid.e

cc. Very short fleas; flagellum of the antenna with pseudo-segments coales-
cent; thorax much shorter than the head and than the first tergite

. HECTOPSYLLID.E

Flagellum of the antenna with six coalescent pseudo-segments; maxilla

blunt. The chigger on man (fig. 93). D. penetrans.

. (= Rhynchoprion = Sarcopsylla) Dermatophilus Guerin

bb. Flagellum short, round, free portion of the first segment shaped like a
mandolin.

c. Thorax not shorter than the head, longer than the first tergite; flagellum
either with free segments or in part with the segments coalescent.

d. Head and pronotum with ctenidium; labial palpi asymmetrical. . . .

. ARCHjEOPSYLLIDjE

With four subfrontal, four genal, and one angular ctenidia. Widely

distributed . Ctenocephalus Kol.

e. Head rounded in front (fig. 92a). Dog flea . C. canis

ee. Head long and flat (fig. 92b). Cat flea . C. felis

dd. Neither head nor pronotum with ctenidium. Labial palpi asym¬
metrical, membranous behind . PULICID.®

e. Mesosternite narrow, without internal rod-like thickening from the

insertion of the coxae upwards. Human flea, etc.Pulex L.

ee. Mesosternite broad with a rod-like internal thickening from the
insertion of the coxae upwards (fig. 89). X. (Loemopsylla) cheopis,

plague or rat flea. Xenopsylla

cc. Thorax much shorter than the head and than the first tergite. Echi-
dnophagidae. E. gallinacea, the hen flea also attacks man (fig. 96).
.(= Argopsylla =Xestopsylla) Echidnophaga 011 iff_

APPENDIX

HYDROCYANIC ACID GAS AGAINST HOUSEHOLD INSECTS

The following directions for fumigating with hydrocyanic acid
gas are taken from Professor Herrick’s circular published by the
Cornell Reading Course:

Hydrocyanic acid gas has been used successfully against house¬
hold insects and will probably be used more and more in the future.
It is particularly effective against bed-bugs, and cockroaches, but
because it is such a deadly poison it must he used very carefully.

The gas is generated from the salt potassium cyanid, by treating
it with sulfuric acid diluted with water. Potassium cyanid is a
most poisonous substance and the gas emanating from it is also
deadly to most, if not all, forms of animal life. The greatest care
must always be exercised in fumigating houses or rooms in buildings
that are occupied. Before fumigation a house should be vacated.
It is not necessary to move furniture or belongings except brass or
nickel objects, which may be somewhat tarnished, and butter, milk,
and other larder supplies that are likely to absorb gas. If the nickel
and brass fixtures or objects are carefully covered with blankets
they will usually be sufficiently protected.

There may be danger in fumigating one house in a solid row of
houses if there is a crack in the walls through which the gas may find
its way. It also follows that the fumigation of one room in a house
may endanger the occupants of an adjoining room if the walls be¬
tween the two rooms are not perfectly tight. It is necessary to keep
all these points in mind and to do the work deliberately and thought¬
fully. The writer has fumigated a large college dormitory of 253
rooms, once a year for several years, without the slightest accident
of any kind. In order to fumigate this building about 340 pounds
of cyanid and the same amount of sulfuric acid were used each time.
In addition to this, the writer has fumigated single rooms and smaller
houses with the gas. In one instance the generating jars were too
small; the liquid boiled over and injured the floors and the rugs.
Such an accident should be avoided by the use of large jars and by
placing old mgs or a quantity of newspapers beneath the jars.

The Proportions of Ingredients

3i9

Experiments and experience have shown that the potassium
cyanid should be ninety-eight per cent pure in order to give satis¬
factory results. The purchaser should insist on the cyanid being of
at least that purity, and it should be procurable at not more than
forty cents per pound. The crude form of sulfuric acid may be used.
It is a thickish, brown liquid and should not cost more than four or
five cents a pound. If a room is made tight, one ounce of cyanid for
every one hundred cubic feet of space has been shown to be sufficient.
It is combined with the acid and water in the following proportions:

Potassium cyanid. 1 ounce

Commercial sulfuric acid. 1 fluid ounce

Water. 3 fluid ounces

A Single Room as an Example

Suppose a room to be 12 by 15 by 8 feet. It will contain
12x15x8, or 1440 cubic feet. For convenience the writer always
works on the basis of complete hundreds; in this case he would
work on the basis of 1500 cubic feet, and thus be sure to have enough.
The foregoing room, then, would require 15 ounces of cyanid, 15
ounces of sulfuric acid, and 45 ounces of water. The room should
be made as tight as possible by stopping all the larger openings,
such as fireplaces and chimney flues, with old rags or blankets.
Cracks about windows or in other places should be sealed with narrow'
strips of newspaper well soaked in water. Strips of newspaper two
or three inches wide that have been thoroughly soaked in water may
be applied quickly and effectively over the cracks around the window
sash and elsewhere. Such strips wall stick closely for several hours
and may be easily removed at the conclusion of the work.

While the room is being made tight, the ingredients should be
measured according to the formula already given. The water should
be measured and poured first into a stone jar for holding at least two
gallons. The jar should be placed in the middle of the room, with
an old rug or several newspapers under it in order to protect the floor.

The required amount of sulfuric acid should then be poured
rather slowly into the w r ater. This process must never he reversed;
that is, the acid must never he poured into the jar first. The cyanid
should be weighed and put into a paper bag beside the jar. All hats,
coats, or other articles that wall be needed before the work is over

320 Hydrocyanic Acid Gas Against Household Insects

should be removed from the room. When everything is ready the
operator should drop the bag of cyam'd gently into the jar, holding
his breath, and should walk quickly out of the room. The steam¬
like gas does not rise immediately under these conditions, and ample
time is given for the operator to walk out and shut the door. If
preferred, however, the paper bag may be suspended by a string
passing through a screw eye in the ceiling and then through the key¬
hole of the door. In this case the bag may be lowered from the out¬
side after the operator has left the room and closed the door.

The writer has most often started the fumigation toward evening
and left it going all night, opening the doors in the morning. The
work can be done, however, at any time during the day and should
extend over a period of five or six hours at least. It is said that bet¬
ter results will be obtained in a temperature of 70° F., or above, than
at a lower degree.

At the close of the operation the windows and doors may be opened
from the outside. In the course of two or three hours the gas should
be dissipated enough to allow a person to enter the room without
danger. The odor of the gas is like that of peach kernels and is easily
recognized. The room should not be occupied until the odor has
disappeared.

Fumigating a Large House

The fumigation of a large house is merely a repetition, in each room
and hall, of the operations already described for a single room. All
the rooms should be made tight, and the proper quantities of water
and sulfuric acid should be measured and poured into jars placed
in each room with the cyanid in bags besides the jars. When all
is ready, the operator should go to the top floor and work doivnward
because the gas is lighter than air and tends to rise.

Precautions

The cyanid should be broken up into small pieces not larger than
small eggs. This can best be done on a cement or brick pavement.
It would be advantageous to wear gloves in order to protect the hands,
although the writer has broken many pounds of cyanid without any
protection on the hands. Wash the hands thoroughly at frequent
intervals in order to remove the cyanid.

The operations of the work must be carried out according to
directions.

Precautions

321

The work should be done by a calm, thoughtful and careful
person—best by one who has had some experience.

Conspicuous notices of what has been done should be placed on
the doors, and the doors should be locked so that no one can stray
into the rooms.

The gas is lighter than air, therefore one should always begin in the
rooms at the top of the house and work down.

After fumigation is over the contents of the jar should be emptied
into the sewer or some other safe place. The jars should be washed
thoroughly before they are used again.

It must be remembered that cyanid is a deadly poison; but it is
very efficient against household insects, if carefully used, and is not
particularly dangerous when properly handled.

LESIONS PRODUCED BY THE BITE OF THE BLACK-FLY

While this text was in press there came to hand an important paper
presenting a phase of the subject of black fly injury so different from
others heretofore given that we deem it expedient to reproduce here
the author’s summary. The paper was published in The Journal
of Cutaneous Diseases, for November and December, 1914, under the
title of “A Clinical, Pathological and Experimental Study of the
Lesions Produced by the Bite of the Black Fly” ( Simulium venus-
tum),” by Dr. John Hinchman Stokes, of the University of Michigan.

Resume and Discussion of Experimental Findings

The principal positive result of the work has been the experimental
reproduction of the lesion produced by the black-flv in characteristic
histological detail by the use of preserved flies. The experimental
lesions not only reproduced the pathological pictures, but followed
a clinical course, which in local symptomatology especially, tallied
closely with that of the bite. This the writer interprets as satis¬
factory evidence that the lesion is not produced by any living infec¬
tive agent. The experiments performed do not identify the nature
of the toxic agent. Tentatively they seem to bring out, however,
the following characteristics.

1. The product of alcoholic extraction of flies do not contain
the toxic agent.

2. The toxic agent is not inactivated by alcohol.

3. The toxic agent is not destroyed by drying fixed flies.

4. The toxic agent is not affected by glycerin, but is, if anything,
more active in pastes made from the ground fly and glycerin, than
in the ground flies as such.

322 Lesions Produced by the Bite of the Black-fly

5. The toxic agent is rendered inactive or destroyed by hydro¬
chloric acid in a concentration of 0.25%.

6. The toxic agent is most abundant in the region of the ana¬
tomical structures connected with the biting and salivary apparatus
(head and thorax).

7. The toxic agent is not affected by a 0.5 % solution of sodium
bicarbonate.

8. The toxic agent is not affected by exposure to dry heat at
ioo° C. for two hours.

9. The toxic agent is destroyed or rendered inactive in alkaline
solution by a typical hydrolytic ferment, pancreatin.

10. Incomplete experimental evidence suggests that the activity
of the toxic agent may be heightened by a possible lytic action of
the blood serum of a sensitive individual, and that the sensitive serum
itself may contain the toxic agent in solution.

These results, as far as they go (omitting No. 10), accord with
Langer’s except on the point of alcoholic solubility and the effect
of acids. The actual nature of the toxic agent in the black-fly is
left a matter of speculation.

The following working theories have suggested themselves to
the writer. First, the toxin may be, as Langer believes in the case
of the bee, an alkaloidal base, toxic as such, and neutralized after
injection by antibodies produced for the occasion by the body. In
such a case the view that a partial local fixation of the toxin occurs,
which prevents its immediate diffusion, is acceptable. Through
chemotactic action, special cells capable of breaking up the toxin
into harmless elements are attracted to the scene. Their function
may be, on the other hand, to neutralize directly, not by lysis.
This would explain the role of the eosinophiles in the black-fly lesion.
If their activities be essential to the destruction or neutralization
of the toxin, one would expect them to be most numerous where
there was least reaction. This would be at the site of a bite in an
immune individual. A point of special interest for further investiga¬
tion, would be the study of such a lesion.

Second, it is conceivable that the injected saliva of the fly does
not contain an agent toxic as such. It is possible, that like many
foreign proteins, it only becomes toxic when broken down. The
completeness and rapidity of the breaking down depends on the
number of eosinophiles present. In such a case immunity should
again be marked by intense eosinophilia.

173. Fifth day mature lesion. Lower power drawing showing papillary oedema and infiltrate in the region
of the puncture.

Lesions Produced by the Bite of the Black-fly

323

324 Lesions Produced by the Bite of the Black-fly

Third, lytic agents in the blood serum may play the chief role
in the liberation of the toxic agent from its non-toxic combination.
An immune individual would then be one whose immunity was not
the positive one of antibody formation, but the negative immunity
of failure to metabolize. An immune lesion in such a case might
be conceived as presenting no eosinophilia, since no toxin is liberated.
If the liberation of the toxin is dependent upon lytic agents present
in the serum rather than in any cellular elements, a rational explana¬
tion would be available for the apparent results (subject to con¬
firmation) of the experiment with sensitive and immune sera. In
this experiment it will be recalled that the sensitive serum seemed to
bring out the toxicity of the ground flies, and the serum itself seemed
even to contain some of the dissolved or liberated toxin. The
slowness with which a lesion develops in the case of the black-fly
bite supports the view of the initial lack of toxicity of the injected
material. The entire absence of early subjective symptoms, such
as pain, burning, etc., is further evidence for this view. It would
appear as if no reaction occurred until lysis of an originally non¬
toxic substance had begun. Regarding the toxin itself as the chemo-
tactic agent which attracts eosinophiles, its liberation in the lytic
process and diffusion through the blood stream attracts the cells
in question to the point at which it is being liberated. Arriving
upon the scene, these cells assist in its neutralization.

The last view presented is the one to which the author inclines
as the one which most adequately explains the phenomena.

A fourth view is that the initial injection of a foreign protein by
the fly (i.e.,with the first bite) sensitizes the body to that protein.
Its subsequent injection at any point in the skin gives rise to a
local expression of systematic sensitization. Such local sensitization
reactions have been described by Arthus and Breton, by Ham¬
burger and Pollack and by Cowie. The description of such a lesion
given by the first named authors, in the rabbit, however, does not
suggest, histopathologieally at least, a strong resemblance to that
of the black-fly. Such an explanation of many insect urticaria
deserves further investigation, however, and may align them under
cutaneous expressions of anaphylaxis to a foreign protein injected
by the insect. Depending on the chemical nature of the protein
injected, a specific chcmotactic reaction like eosinophilia may or
may not occur. Viewed in this light the development of immunity
to insect bites assumes a place in the larger problem of anaphylaxis.

Lesions Produced by the Bite of the Black-fly

325

174. Experimentaljesion produced from alcohol-fixed flies, dried and ground into a
paste with glycerin.

326 Lesions Produced by ike Bite of the Black-fly

Summary

In order to bring the results of the foregoing studies together,
the author appends the following resume of the clinical data pre¬
sented in the first paper.

The black-fly, Simulium venustum , inflicts a painless bite, with
ecchymosis and haemorrhage at the site of puncture. A papulo¬
vesicular lesion upon an urticarial base slowly develops, the full
course of the lesion occupying several days to several weeks. Marked
differences in individual reaction occur, but the typical course in¬
volves four stages. These are, in chronological order, the papular
stage, the vesicular or pseudovesicular, the mature vesico-papular or
weeping papular stage and the stage of involution terminating in a
scar. The papule develops in from 3 to 24 hours. The early pseudo¬
vesicle develops in 24 to 48 hours. The mature vesico-papular lesion
develops by the third to fifth day and may last from a few days to
three weeks. Involution is marked by cessation of oozing, subsidence
of the papule and sear-like changes at the site of the lesion. The
symptoms accompanying this cycle consist of severe localized or
diffused pruritus, with some heat and burning in the earlier stages
if the oedema is marked. The pruritus appears with the pseudo¬
vesicular stage and exhibits extraordinary persistence and a marked
tendency to periodic spontaneous exacerbation. The flies tend to
group their bites and confluence of the developing lesions in such
cases may result in extensive oedema with the formation of oozing
and crusted plaques. A special tendency on the part of the flies
to attack the skin about the cheeks, eyes and the neck along the
hair line and behind the ears, is noted. In these sites inflammation
and oedema may be extreme.

A distinctive satellite adeonpathy of the cervical glands develops
in the majority of susceptible persons within 48 hours after being
bitten in the typical sites. This adenopathy is marked, discrete
and painful, the glands often exquisitely tender on pressure. It
subsides without suppuration.

Immunity may be developed to all except the earliest manifesta¬
tions, by repeated exposures. Such an immunity in natives of an
infested locality is usually highly developed. There are also ap¬
parently seasonal variations in the virulence of the fly and variations
in the reaction of the same individual to different bites.

Constitutional effects were not observed but have been reported.

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INDEX

Abscess . 178

Acanthia . 87

Acariasis . 58

Acarina . 23, 58, 131, 259

Acarus dysenteriae . 132

Accidental parasites . 131, 132, 134

Aedes . 194, 293

Aedes calopus. .. 182, 201, 205, 206, 208

Aedes cantator . 101

Aedes sollicitans . 101

Aedes tceniorhynchus . 101

Aerobic bacteria . 152

Aestivo-autumnal . 186

African Relapsing Fever . 230

Akis spinosa . 177

Alternation of Generations . 175

Amblyomma . 264

Amblyomma americanum . 67

Amblyomma cajennense . 67

American dog tick . 228

Amoeboid organism . 189

Anisolabis annulipes . 177

Anterior poliomyelitis . 241

Anopheles . 194, 291

Anopheles crucians . 199

Anopheles maculipennis . 182

Anopheles punctipennis . 198

Anopheles quadrimaculatus . 197

Anopheline . 192

Anthocoris . 279

Anthomyiidae . 300

Anthomyia . 138

Anthrax . 165

Antipruritic treatment . 72

Ants . 42

Aphiochaeta . 295

Apis mellifica . 36

Arachnida . 258

Araneida . 6

Argas . 64

Argas persicus .. .63, 235, 237

Argasidae . 62

Argopsylla . 317

Argus . 259

341

PACE

Arilus.

Arthopods, poisonous. . . .

. 6

Asopia farinalis.

. 177

Assassin-bugs.

. 31. 219

Auchmeromyia.

. 1 17

Automeris io.

. 47

Avicularoidea.

. 12

Babesia .

Babesia bovis .

. 223

Babesia ovis.

. 225

Babesiosis .

Bacilli.

. 170

Bacillus icteroides .

....202, 205

Bacillus pestis.

. 166

Bacillus typhosus.

. 153

Back swimmers .

. 30

Bdellolarynx.

. 304

Beauperthuy, Louis Daniel. 2

Bed-bug.86, 88, 90,

173,219-220

Bed-bug, cone-nosed.

. 92

Blister beetles .

. 54

Belostoma.

. 28, 277

Belostoma americana . .. .

. 3 i

Belostomatidae .

. 30

Bengalia.

. 314

Bird-spiders .

. 10

Black death.

.1, 166

Black flies .

.33, 104, 247

Black heads.

Blaps mortisaga.

. 134

Blepharoceridae.

. 286

Boophilus .

. 264

Boophilus annulatus.

.67, 223-225

Bot-flies.

. 112

Blue bottle flies.

. 140

Brill’s disease.

. 238

Brown-tailed moth.

. 48

Bruck.

. 34

Buthus quinquestriatus . .

. 21

Cabbage butterfly.

. 56

Calliphora .

136,140, 312

Calliphora erythrocephala

. Hi

342

Index

Calobata .

296

Compsomyia .

. 117

Camponotinae.

Cone-nosed bed-bug ....

. 92

Cancer .

254

Conjunctivitis, nodular.

. 52

Cantharidin.

Conorhinus .

. 282

Cantharidin poison.

Conorhinus megistus. . . .

.93,219-220

Canthariasis .

134

Conorhinus rubrofasciatus . 220

Capsidae.

280

Conorhinus sanguisugus.

. 32, 92

Carriers, simple.

■ • - 4 .

144

Copra itch.

. 72

Carriers of disease .

144

Cordylobia .

. 118

Carrion’s fever.

253

Coriscus.

. 280

Caterpillar rash.

Coriscus subcoleoptratus

. 32

Cat flea .

172

Creeping myasis .

. 112

Cattle ticks.

222

Crustacea .

. 257

Causative organism.

170

Cryptocystis .

. 176

Cellia .

291

Cryptotoxic .

. 54-55

Centipedes.

• 25,

257

Cteniza sauvagei .

. 13

Ceratophyllus.

120,

316

Ctenocephalus . 120,

172, 213,317

Ceratophyllus acutus .

123

Culex .

194,201, 293

Ceratophyllus fasciatus ..122

172,

213

Culex pipiens .

. 35 , 98

Ceratopogon.

108

Culex quinquefasciatus. .

. 180

Cheese-fly .

137

Culex sollicitans .

. 200

Cheyletus eruditus .

271

Culex territans .

. IOI

Chigger .

. . .60, 70

Culicidae .

. 33 , 97

Chigoes .

126

Culicin .

. 34

Chilopoda .

• -25,

257

Culicoides .

.... 109, 288

Chiracanthium nutrix .

Cyclops .

.... l8^. 2 S 7

Chironomidae .

107

Cynomyia .

— 136,311

Chorioptes.

270

Chrysomelid.

Dance, St. Vitus .

. 8

Chrysomyia.

136, 308

Dancing mania .

. 8

Chrysomyia macellaria .

•ii 7 .

140

Deer-flies .

. IIO

Chrysops .

294

Definitive host.

. 192

Chylous dropsy.

179

Demodecidae .

. 78

Chyluria .

178

Demodex .

. 259

Cicadidae .

Demodex folliculorum . . .

. 78

Cimex L .

278

Dermaeentor .

. 262

Cimex boueti .

Dermacentor andersoni . .

iC.

Cimex columbarius .

Dermaeentor occidentalis.

. 227

Cimex hemipterus.

91.

220

Dermacentor variabilis. . .

. 67

Cimex hirundinis .

Dermacentor venustus . . .

. 24, 228

Cimex inodorus .

Dermanyssidae .

. 68

Cimex lectularius .

.. 87,219

Dermanyssus .

. 266

Citheronia regalis .

Dermanyssus gallinas . . . .

. 68

Clinocoris .

Dermatitis .

• - 72 , 77 , 85

Coleoptera .

134 .

274

Dermatobia .

...IIS, 298

Comedons .

Dcrmatobia cyaniventris .

. 163

Complete metamorphosis ....

Dermatophilus .

. 317

Compressor muscle .

Dermatophilus penetrans .

. 60, 126

Index

343

Diamphidia simplex . 55

Dimorphism . 65

Direct inoculators . 4

Diplopoda. . , . .. 25, 257

Diptera . 33, 94, 274

Dipterous Larvae . 135

Dipylidium . 175,221

Dipylidium canium . 4, 175-176

Dog flea . 172

Dracunculus . 257

Dracunculus medinensis . 182

Drosophila . 296

Dum-dum fever . 220

Dysentery . 154

Ear-flies . no

Earwig . 177

Echidnophaga . 317

Echinorynchus . 185

Elephantiasis . 178-179

Empoasca mali . 33

Empretia . 46

English Plague Commission . 171

Epeira diadema . 18

Epizootic . 170

Eristalis . 137,295

Essential hosts. 4, 165

Eumusca . 307

European Relapsing Fever . 233

Euproctis chrysorrhoea . 48

Eusimulium . 286

Facultative parasites . 131

Fannia . 136, 138, 145, 300

Federal Health Service . 169

Fever, lenticular . 237

African Relapsing . 230, 234

Carrion’s . 253

dum-dum . 154

European Relapsing. 233

pappatici . 96

red water . 220

Rocky Mt. Spotted. 226

three day . 96

Typhus . 237

Filaria . 178, 221

immitis . 182

Filariasis . 178

Flannel-moth larvae.

. 44

Fleas .

119, 166, 213

cat .

. 172

dog .

. 172

human.

.... 172, 176

rodent .

.... 123, 172

rat .

. 171

Flesope.

. 125

Formaldehyde .

. 91

Fomites .

. . . . 199, 204

Fulgoridae .

. 28

Fumigation .

. 320

Gamasid .

. 68

Gangrene .

. 129

Gastrophilus.

. 1 13,297

Giant crab spiders.

. 13

Giant water bugs.

. 30

Gigantorhynchus.

. 185

Glossina.

117, 297, 303

Glossina morsitans.

.... 214, 217

palpalis.

215, 217, 218

Glyciphagus .

. 267

Grain moth .

. 69

Grocer’s itch.

. 72

Guinea-worm .

. 182

Habronema muscae .

156, 183

Haematobia .

. 166, 304

irritans.

. 146

Haematobosca .

. 304

Haematomyidium.

. 288

Haematopinus spinulosus

. 213

Haematopota .

. 294

Haematosiphon .

. 279

Haemoglobinuria .

. 220

Haemozoin .

. 189

Harpactor.

. 284

Harvest mites .

. 60

effect of.

. 39

Head-louse .

. 173

Helminthiasis.

. 138

Helophilus .

. 295

Hemiptera . 27

, 86, 273-275

Heteropodidae.

. 13

Heuchis sanguinea.

. 55

Hexapod larvae.

. 58

Hexapoda .

...27, 80,258

344

Index

Hippelates . 297

Hippobosca . 285

Histiogaster . 269

spermaticus . 132

Homalomyia . 136, 138,300

Honey bee . 36

poison of . 37

Hornets . 43

Horn-fly . 137, 304, 308

Horse-fly . no, 165

House-fly . I 37 -I 39 . 144 . 183

control of . 156, 160

Human flea .. 124

Host, definitive . 175

intermediate . 175

primary . 175

Hyalomma . 264

aegypticum . 224-225

Hydrocyanic Acid Gas . 318

Hydrotaea . 300

Hymenolepis diminuta . 176

Hymenoptera . 36, 275

Hypoderma . 113, 298

diana . 113

lineata . 113

Hypopharynx . 80

Jigger . 60

Johannseniella . no, 288

Journal of Tropical Medicine and

Hygiene . 36

Julusterrestris . 25

June bug . 185

Kala-azar . 220

Kara, kurte . 14

Katipo . 14

King, A. F. A . 3

Kircher, Athanasius . 1, 8

Kissing-bug . 31

Labium . 29, 80

Labrum . 28, 80

Lachnosterna . 185

Laelaps . 266

Lcemopsylla . 172

Lagoa crispata . 45

Lamblia intestinalis . 154

Langer, Josef . 37

Larder beetles . 135

Latrodectus . 12, 14, 17

mactans . 15

Leishmanioses . 220

Lenticular fever . 237

Lepidoptera . 274

Lepidopterous larvae . 134

Leprosy . 252

Leptidae . 112

Leptis . 295

Leptus . 60, 273

Lice . 80

Linguatulina . 258

Liponyssus . 265

Lone star tick . 228

Louse, body . 84

crab . 85

dog . 176

head . 82

pubic . 85

Lcemopsylla . 172, 317

Lucilia . 136, 312

Lycosa tarantula . 10

Lycosidae . 10

Lyctocoris . 279

Lygus pratensis. 33

Immunity from stings . 39

Incomplete metamorphosis . 80

Infantile paralysis.162,241

splenic . 220

Direct inoculation . 164

Insects . 258

blood-sucking . 170

Intermediate host . 192, 203

Intestinal infestation . 112, 133

myasis . 137

Isosoma . 69

Itch . 73-74

mite . 73

Norwegian. 77

Ixodes . 260

ricinus. 66, 225

scapularis. 66

Ixodidae. 64-65

Ixodoidea. 62

Janthinosoma lutzi. 116

Index

345

Lymphangitis . 67

Lymph scrotum . 178

Lyperosia . 304

Lyperosiops . 305

Macloskie . 34

Maggots, rat-tail . 137

Magnes sive de Arte Magnetica. . 8

Malaria . 186

Malmigniatte . 14

Mandibles . 28, 80

Mange . 73-75

Margaropus . 237, 264

annulatus . 223

Masked bed-bug hunter . 32

Mastigoproetus giganteus . 19, 80

Maxillae . 28

Meal infesting species . 135

Melanin granules . 189

Melanolestes .. 280

picipes . 32

Mena-vodi . 14

Mercurialis . 1

Merozoites . 190

Metamorphosis . 80

Miana bug . 63

Microgametoblast . 192

Midges . 107

Migratory ookinete . 192

Millipedes . 25, 257

Mites . 23, 58

Monieziella . 269

Mosquitoes . 33,97. 178, 196, 250

treatment for bites of. . . .34, 36, 102

Musca . 137,307

domestica. . . . 139, 145, 146, 157, 162

Muscidae . 117

Muscina . 137, 146, 307

stabulans . 140

Mutualism . 57

Myasis . 112, 135

intestinal . 13 5-140

nasal . 141

Mycterotypus . 287

Myiospila . 146,307

Myriapoda . 25,132,257

Nagana . 165,214

Nasal infestation . 114, 133

Necrobia . 135

Nematode parasite . 182

Nepa . 28

Nephrophages sanguinarius . 132

Nettling insects . 43

larvae, poison of . 53

N eurasthenia . 89

Nits . 86

North African Relapsing Fever. . 234

Norwegian itch . 77

No-see-ums . 109

Notoedres . 269

cati . 78

Notonecta . 28, 277

Notonectidae . 30

Nott, Dr. Josiah . 2

Nuttall . 34

Occipital headaches . 138

Oecacta . 288

Oeciacus . 279

CEsophageal diverticula. 35

Oestridae . 112,136

Oestris ovis . 113

Oestrus . 298

oocyst . 192

ookinete . 192

Opsicoetes personatus . 32

Opthalmia . 155

nodosa . 52

Oriental sore . 221

Omithodoros . 65, 260

moubata . 220, 230

Orthotvlus flavosparsus . 33

Ornithomyia . 286

Oroya . 253

Oscinus . 297

Otiobius . 259

megnini . 65

Otodectes . 271

Pangonia . 294

Pappatici fever. 96

Parasimulium . 286

Parasite . r. .3, 57, 131, 134, 182

accidental . 3, 131, 134

facultative. 3, 57, 131

346

Index

Parasite, nematode . 182

stationary . 57

temporary . 57

true . 3

Parasitism, accidental . 134

Pathogenic bacteria . 152

organisms . 144, 164

Pawlowsky . 81

Pediculoides . 267

ventricosus . 69, 72

Pediculosis . 81

Pediculus . 275

corporis . 84, 233, 238

humanus . 82, 173

Pellagra . 162, 246

Pernicious fever . 186

Pest . 166

Phidippus audax . 19

Philsematomyia . 306

Phisalix . 13.43

Phlebotomus . 289

papatasii . 94

verrucarum . 254

vexator . 95

Phora . 295

Phormia . 136

Phormictopus carcerides . 13

Phthirus pubis . 85, 275

Phortica . 296

Pieris brassicae . I.'V ! 56

Piophila . 297

Piophila casei . 136, 137

Piroplasmosis . 222

Plague . 166

bubonic . 166, 169, 170

pneumonic . 167

Plasmodium . 186

Platymetopius acutus . 33

Plica palonica . 83

Pneumonic . 166

plague . 167, 173

Poisoning by nettling larvas. 53

Poison of spiders . 7

Pollenia . 308

rudis . 146, 147

primary gland . 28

Prionurus citrinus . 20

Prosimulium . 286

Protocalliphora . 136, 312

Protozoan blood parasite . 165

Pseudo-tubercular . 52

Psorophora . 293

Psoroptes . 270

Psychodidag . 94

Pulex . 120, 124, 126, 172,317

cheopis . 172

irritans . 124

penetrans . 126

serraticeps . 120

Pulvillus . 150

Punkies . 109

Pycnosoma . 308

Rasahus . 280

thoracicus . 32

Rat fleas . 120, 124,171

Rat louse . 213

Red bugs . 70-72

Reduviidae . 31

Reduviolus . 280

Reduvius . 282

personatus . 32

Red water fever . 220

Relapsing fever . 230, 233

Rhinoestrus nasalis . 115

Rhipicentor . 264

Rhipicephalus . 264

Rhizoglyphus . 269

Rhodnius . 280

Rocky Mountain Spotted Fever. . 226

spotted fever tick . 67

Russian gad-fly . 115

St. Vitus’s or St. John’s dance. ... 8

Salivary syringe . 28

Sand-flies . 109, 250

Sanguinetti . 11

Sarcophaga . 136, 142, 143

Sarcophila . 302

Sarcopsylla . 317

penetrans . 126

Sarcoptes . 270

minor . 78

scabiei . 73

Sarcoptidae . 72

Scabies. 72, 73, 74, 75

Index

Scaurus striatus . 177

Schaudinn . 34

Schizont . 189, 190

Scholeciasis . 134

Scolopendra morsitans .. 26

Scorpions . 20

poison of . 21

Screw worm fly . 140

Sepsidse . 296

Sepsis . 136, 297

Shipley . 34

Sibine . 46

Silvius . 294

Simple carriers . 4, 144

Simuliidae . 33, 104

Simulium . 247, 249, 286, 321

pictipes . 104

Siphonaptera . 119, 274, 316

Siphunculata . 80, 275

Sitotroga cerealella . 69

Skippers . 137

Sleeping sickness . 166, 215

Snipe-flies . 112

Solpugida . 22

Spanish fly . 54

Spermatozoa . 192

Spinose ear-tick . 65

Spirochoeta . 35

berberi . 234

duttoni . 234

Spirochaetosis . 235

Sporozoite . 189

Spotted fever . 67, 226

Squirrel flea . 123

Stable-fly . 137, 160, 163, 165

Stegomyia . 182, 293

calopus . 206

fasciata . 206

Stomoxys . 137, 305

calcitrans 117, 146, 160, 161, 165, 242

Straw-worm . 69

Stygeromyia. 305

Sucking stomach. 35

Sulphur ointment. 77

Surra . 165

Symbiosis . 57

Symphoromyia. 112, 295

347

Tabanidae . no

Tabanus . no, 166, 294

striatus . 165

Taenia . 175

Tapeworm . 4, 176

Tarantella . 8

Tarantism . 8

Tarantula . 10

Tarsonemidae . 69

Tarsonemus . 267

Tenebrionid beetles . 127

Tersesthes . no, 288

Tetanus . 129

Tetranychus . 273

Texas fever . 220-223

Three-day fever . 96

Tick . 23, 226

bites, Treatment of . 68

fever . 230

paralysis . 67

Treatment,

Bee stings . 36, 41

Bites of,

Bed-bugs . 90,93

Blackflies . 107

Buffalo flies . 107

Bugs . 31, 33

Centipedes . 26, 27

Chiggers . 127

Chigoes . 127

Fleas . 127

Harvest mites . 61

Jiggers . 129

Lice . 83,85

Mosquitoes . 34, 36, 102

Phlebotomus flies . 97

Sand flies . 96, 107, 109

Scorpions . 22,23

Spiders . 19

Ticks . 61,68,72

Ticks, ear . 65

Blister beetle poison . 55

Brown-tail moth rash . 45

Cantharidin poison . 55

Caterpillar rash . 45

Ear ticks . 65

House fly control . 156, 160

Itch . 77

348

Index

Itch, grocer’s . 72

Lice . 85

Nasal myasis . 143

Rocky Mt. spotted fever. . .228, 229

Rash, caterpillar . 45

Scabies . 77

Sleeping sickness control . 218

Spotted fever . 228, 229

Stings, bee . 36, 41

Typhus fever, prophylaxis . 239

Trichodectes canis . 176

Trichoma . 82

Trineura .. 295

Trochosa singoriensis . 11

Trombidium . 60, 273

True insects . 80

T ry panosoma . 35

Trypanosoma, brucei . 165

Trypanosoma cruzi . 219

Trypanosoma lewisi . 213

Trypanosomiases . 212

Trypanosomiasis . 165,219

Testse flies . 117, 166, 214, 219

Tsetse flies disease . 165

T uberculosis . 155

Tumbu-fly . 118

Tydeus . 271

Typhoid . 155

Typhoid fever . 154

Typhus . 237

Typhus fever . 237

Tyroglyphus . 72, 131, 268

Dr. Tyzzer . 49

Uranotaenia . 292

Vancoho . 14

Varicose groin glands . 178

Verruga peruviana . 253

Vescicating insects . 54

Wanzenspritze . 29

Warble-flies . 112

Wasps .. 43

Whip-scorpions . 19

Wohlfahrtia . 143, 302

Wolf-spiders . 10

Wyeomyia smithii . 101, 293

Xenopsylla . 172, 317

Xenopsylla cheopis . 171, 124

Xestopsylla . 317

Yaws . 2

Yellow fever . 196, 203, 205

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